javascript-obfuscator
Version:
JavaScript obfuscator
2,557 lines • 107 kB
Markdown
<!--
Title: JavaScript Obfuscator
Description: A powerful obfuscator for JavaScript and Node.js.
Author: Timofei Kachalov
-->
# JavaScript obfuscator
---
### :rocket: Obfuscator.io with VM Obfuscation
[](https://obfuscator.io)
**Obfuscator.io** adds **VM-based bytecode obfuscation** to this package - your JavaScript functions are compiled to custom bytecode that runs on an embedded virtual machine. Each build produces unique opcodes and VM structure, making reverse engineering and automated deobfuscation dramatically harder.
| Protection goal | Free (this package) | [obfuscator.io](https://obfuscator.io) |
| --- |-----------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Rename identifiers | ✅ variable/function renaming | ✅ + VM-local symbols never exposed as JavaScript |
| Obscure strings | ✅ string array + base64/rc4 | ✅ + strings embedded in bytecode constants |
| Obscure control flow | ✅ control flow flattening | ✅ full bytecode virtualization, [`vmJumpsEncoding`](#vmjumpsencoding) (runtime-computed jump targets), [`vmDeadCodeInjection`](#vmdeadcodeinjection) (fake bytecode sequences) |
| Resist decompilation | ⚠️ output is still JavaScript | ✅ custom opcodes, [`vmStatefulOpcodes`](#vmstatefulopcodes) (position-dependent opcode mapping), [`vmMacroOps`](#vmmacroops) (fused instructions), [`vmDecoyOpcodes`](#vmdecoyopcodes) (fake opcode handlers) |
| Resist automated LLM-based analysis | ❌ fully vulnerable (no LLM-specific defenses) | ✅ bytecode encryption + anti-LLM defenses in [`vmSelfDefending`](#vmselfdefending) and [`vmDebugProtection`](#vmdebugProtection) |
| Encryption | ✅ [`stringArrayEncoding`](#stringarrayencoding) (base64/rc4 on extracted strings) | ✅ [`vmBytecodeEncoding`](#vmbytecodeencoding) (per-instruction encoding), [`vmBytecodeArrayEncoding`](#vmbytecodeArrayEncoding) (whole bytecode array as single block) |
| Anti-debugging | ✅ `debugProtection` (freezes browser DevTools) | ✅ [`vmDebugProtection`](#vmdebugProtection) (multi-layered anti-debugging and anti-analysis defenses) |
| Tamper detection | ✅ `selfDefending` (breaks if beautified) | ✅ [`vmSelfDefending`](#vmselfdefending) (multi-layered tamper detection, anti-hooking, anti-reverse-engineering protection) |
| Runs offline, no network | ✅ | ❌ uses obfuscator.io API (requires token) |
[Visit Obfuscator.io](https://obfuscator.io) · [Pro API methods](#shield-pro-api-methods-vm-obfuscation)
This package provides access to Obfuscator.io API via CLI and Node.js API.
---
### Do you use JavaScript Obfuscator at your company?
JavaScript Obfuscator has reached over **1 million npm downloads per week**. I am currently preparing an **EB-1 immigration case** and collecting independent evidence of the project’s real-world professional usage and impact.
If you use JavaScript Obfuscator in a company project — especially at a well-known company, large organization, or widely used product — I would be very grateful if you could contact me.
Helpful evidence may include a brief confirmation or, ideally, a 1–2 page reference letter describing:
- how your team or company used JavaScript Obfuscator;
- why you chose it;
- what problem it helped solve;
- whether it was used in production or an important internal workflow;
- your role and how you are familiar with the usage.
I can provide a simple draft/template to make this easy.
Please contact me at: **referenceletter@obfuscator.io**
Thank you for supporting the project.
---
JavaScript Obfuscator is a powerful free obfuscator for JavaScript, containing a variety of features which provide protection for your source code.
**Key features:**
- VM bytecode obfuscation (via [Obfuscator.io](https://obfuscator.io/))
- variables renaming
- strings extraction and encryption
- dead code injection
- control flow flattening
- various code transformations
- and [more](#javascript-obfuscator-options)...
The example of obfuscated code: [github.com](https://github.com/javascript-obfuscator/javascript-obfuscator/blob/master/examples/javascript-obfuscator.js)
#### Online version:
[obfuscator.io](https://obfuscator.io)
#### Plugins:
* Webpack plugin: [webpack-obfuscator](https://github.com/javascript-obfuscator/webpack-obfuscator)
* Webpack loader: [obfuscator-loader](https://github.com/javascript-obfuscator/obfuscator-loader)
* Esbuild plugin: [esbuild-javascript-obfuscator](https://www.npmjs.com/package/esbuild-javascript-obfuscator)
* Gulp: [gulp-javascript-obfuscator](https://github.com/javascript-obfuscator/gulp-javascript-obfuscator)
* Grunt: [grunt-contrib-obfuscator](https://github.com/javascript-obfuscator/grunt-contrib-obfuscator)
* Rollup: [rollup-plugin-javascript-obfuscator](https://github.com/javascript-obfuscator/rollup-plugin-javascript-obfuscator)
* Weex: [weex-devtool](https://www.npmjs.com/package/weex-devtool)
* Malta: [malta-js-obfuscator](https://github.com/fedeghe/malta-js-obfuscator)
* Netlify plugin: [netlify-plugin-js-obfuscator](https://www.npmjs.com/package/netlify-plugin-js-obfuscator)
* Snowpack plugin: [snowpack-javascript-obfuscator](https://www.npmjs.com/package/snowpack-javascript-obfuscator)
* Vite plugin: [vite-plugin-bundle-obfuscator](https://github.com/z0ffy/vite-plugin-bundle-obfuscator)
[](https://badge.fury.io/js/javascript-obfuscator)
[](https://app.fossa.io/projects/git%2Bgithub.com%2Fjavascript-obfuscator%2Fjavascript-obfuscator?ref=badge_shield)
[](https://coveralls.io/github/javascript-obfuscator/javascript-obfuscator)
[](#backers)
[](#sponsors)
[](https://xscode.com/sanex3339/javascript-obfuscator)
#### *NOTE! the README on the master branch might not match that of the latest stable release!*
#### If you have a question, check this section first: [FAQ](#frequently-asked-questions)
## :warning: Important
##### Only obfuscate the code that belongs to you.
It is not recommended to obfuscate vendor scripts and polyfills, since the obfuscated code is 15-80% slower (depends on options) and the files are significantly larger.
## Installation
#### Using Yarn or NPM
Install the package with Yarn or NPM and add it to your `dependencies` or `devDependencies`:
```sh
$ yarn add --dev javascript-obfuscator
```
or
```sh
$ npm install --save-dev javascript-obfuscator
```
#### In a Browser
From CDN:
```html
<script src="https://cdn.jsdelivr.net/npm/javascript-obfuscator/dist/index.browser.js"></script>
```
From `node_modules`:
```html
<script src="./node_modules/javascript-obfuscator/dist/index.browser.js"></script>
```
## Usage
```javascript
var JavaScriptObfuscator = require('javascript-obfuscator');
var obfuscationResult = JavaScriptObfuscator.obfuscate(
`
(function(){
var variable1 = '5' - 3;
var variable2 = '5' + 3;
var variable3 = '5' + - '2';
var variable4 = ['10','10','10','10','10'].map(parseInt);
var variable5 = 'foo ' + 1 + 1;
console.log(variable1);
console.log(variable2);
console.log(variable3);
console.log(variable4);
console.log(variable5);
})();
`,
{
compact: false,
controlFlowFlattening: true,
controlFlowFlatteningThreshold: 1,
numbersToExpressions: true,
simplify: true,
stringArrayShuffle: true,
splitStrings: true,
stringArrayThreshold: 1
}
);
console.log(obfuscationResult.getObfuscatedCode());
/*
var _0x9947 = [
'map',
'log',
'foo\x20',
'bvmqO',
'133039ViRMWR',
'xPfLC',
'ytpdx',
'1243717qSZCyh',
'2|7|4|6|9|',
'1ErtbCr',
'1608314VKvthn',
'1ZRaFKN',
'XBoAA',
'423266kQOYHV',
'3|0|5|8|1',
'235064xPNdKe',
'13RUDZfG',
'157gNPQGm',
'1639212MvnHZL',
'rDjOa',
'iBHph',
'9926iRHoRl',
'split'
];
function _0x33e4(_0x1809b5, _0x37ef6e) {
return _0x33e4 = function (_0x338a69, _0x39ad79) {
_0x338a69 = _0x338a69 - (0x1939 + -0xf * 0x1f3 + 0x1 * 0x469);
var _0x2b223a = _0x9947[_0x338a69];
return _0x2b223a;
}, _0x33e4(_0x1809b5, _0x37ef6e);
}
(function (_0x431d87, _0x156c7f) {
var _0x10cf6e = _0x33e4;
while (!![]) {
try {
var _0x330ad1 = -parseInt(_0x10cf6e(0x6c)) * -parseInt(_0x10cf6e(0x6d)) + -parseInt(_0x10cf6e(0x74)) * -parseInt(_0x10cf6e(0x78)) + parseInt(_0x10cf6e(0x6a)) + -parseInt(_0x10cf6e(0x70)) + parseInt(_0x10cf6e(0x6e)) * -parseInt(_0x10cf6e(0x75)) + parseInt(_0x10cf6e(0x72)) + -parseInt(_0x10cf6e(0x67)) * parseInt(_0x10cf6e(0x73));
if (_0x330ad1 === _0x156c7f)
break;
else
_0x431d87['push'](_0x431d87['shift']());
} catch (_0x9f878) {
_0x431d87['push'](_0x431d87['shift']());
}
}
}(_0x9947, -0xb6270 + 0x4dfd2 * 0x2 + 0x75460 * 0x2), function () {
var _0x1f346d = _0x33e4, _0x860db8 = {
'ytpdx': _0x1f346d(0x6b) + _0x1f346d(0x71),
'bvmqO': function (_0x560787, _0x519b9e) {
return _0x560787 - _0x519b9e;
},
'rDjOa': function (_0x4501fe, _0x2b07a3) {
return _0x4501fe + _0x2b07a3;
},
'xPfLC': function (_0x5f3c9b, _0x434936) {
return _0x5f3c9b + _0x434936;
},
'XBoAA': function (_0x535b8a, _0x42eef4) {
return _0x535b8a + _0x42eef4;
},
'iBHph': _0x1f346d(0x65)
}, _0x346c55 = _0x860db8[_0x1f346d(0x69)][_0x1f346d(0x79)]('|'), _0x3bf817 = 0x4bb * 0x1 + 0x801 + -0xcbc;
while (!![]) {
switch (_0x346c55[_0x3bf817++]) {
case '0':
console[_0x1f346d(0x7b)](_0x4c96d8);
continue;
case '1':
console[_0x1f346d(0x7b)](_0x101028);
continue;
case '2':
var _0x65977d = _0x860db8[_0x1f346d(0x66)]('5', -0x586 + -0x2195 + -0x6 * -0x685);
continue;
case '3':
console[_0x1f346d(0x7b)](_0x65977d);
continue;
case '4':
var _0x56d39b = _0x860db8[_0x1f346d(0x76)]('5', -'2');
continue;
case '5':
console[_0x1f346d(0x7b)](_0x56d39b);
continue;
case '6':
var _0x544285 = [
'10',
'10',
'10',
'10',
'10'
][_0x1f346d(0x7a)](parseInt);
continue;
case '7':
var _0x4c96d8 = _0x860db8[_0x1f346d(0x68)]('5', 0x622 * -0x6 + 0x4a * 0x3 + 0x1 * 0x23f1);
continue;
case '8':
console[_0x1f346d(0x7b)](_0x544285);
continue;
case '9':
var _0x101028 = _0x860db8[_0x1f346d(0x6f)](_0x860db8[_0x1f346d(0x6f)](_0x860db8[_0x1f346d(0x77)], 0x6fb * 0x5 + 0x1ebf * 0x1 + -0x41a5), 0x209 * 0xa + 0x1314 + -0x276d);
continue;
}
break;
}
}());
*/
```
### `obfuscate(sourceCode, options)`
Returns `ObfuscationResult` object which contains two public methods:
* `getObfuscatedCode()` - returns `string` with obfuscated code;
* `getSourceMap()` - if [`sourceMap`](#sourcemap) option is enabled - returns `string` with source map or an empty string if [`sourceMapMode`](#sourcemapmode) option is set as `inline`;
* `getIdentifierNamesCache()` - returns object with identifier names cache if `identifierNamesCache` option is enabled, `null` overwise.
Calling `toString()` for `ObfuscationResult` object will return `string` with obfuscated code.
Method takes two parameters, `sourceCode` and `options` – the source code and the options respectively:
* `sourceCode` (`string`, default: `null`) – any valid source code, passed as a string;
* `options` (`Object`, default: `null`) – an object with options.
For available options, see [options](#options).
### `obfuscateMultiple(sourceCodesObject, options)`
Accepts `sourceCodesObject` that is a map which keys are identifiers of source codes and values are source codes:
```
{
foo: 'var foo = 1;',
bar: 'var bar = 2;'
}
```
Returns a map object which keys are identifiers of source codes and values are `ObfuscationResult` objects.
### `getOptionsByPreset(optionsPreset)`
Returns an options object for the passed options preset name.
---
## :shield: Pro API Methods (VM Obfuscation)
The Pro API methods provide access to **VM-based bytecode obfuscation** through the [obfuscator.io](https://obfuscator.io) cloud service. VM obfuscation is the most advanced and secure form of code protection available, transforming your JavaScript functions into custom bytecode that runs on an embedded virtual machine.
**Why VM Obfuscation?**
- **Strongest protection**: Code is converted to bytecode that cannot be directly understood
- **Anti-decompilation**: No standard JavaScript to reverse engineer
- **Customizable VM**: Each obfuscation generates unique opcodes and VM structure
- **Layered security**: Combine with other obfuscation options for defense in depth
### Getting an API Token
To use Pro API methods, you need a valid API token from [obfuscator.io](https://obfuscator.io):
1. Create an account at [obfuscator.io](https://obfuscator.io)
2. Subscribe to a Pro, Team, or Business plan that includes API access
3. Generate your API token at [obfuscator.io/dashboard](https://obfuscator.io/dashboard)
### `obfuscatePro(sourceCode, options, proApiConfig, onProgress?)` :new:
**Async method** that obfuscates code using the Pro API with VM-based bytecode obfuscation.
```javascript
const JavaScriptObfuscator = require('javascript-obfuscator');
const result = await JavaScriptObfuscator.obfuscatePro(
`function hello() { console.log("Hello World"); }`,
{
vmObfuscation: true, // Required!
compact: true
},
{
apiToken: 'your_javascript_obfuscator_pro_api_token'
}
);
console.log(result.getObfuscatedCode());
```
**Parameters:**
* `sourceCode` (`string`) – source code to obfuscate
* `options` (`Object`) – obfuscation options. To use the Pro API, include at least one Pro feature: `vmObfuscation: true` or `parseHtml: true`. When no Pro feature is enabled, `obfuscatePro` falls back to the basic (local) obfuscation API.
* `apiConfig` (`Object`) – Pro API configuration:
* `apiToken` (`string`, required) – your API token from obfuscator.io
* `timeout` (`number`, optional) – request timeout in ms (default: `300000` - 5 minutes)
* `version` (`string`, optional) – Obfuscator.io version to use (e.g., `'5.0.3'`). Defaults to latest version if not specified.
* `onProgress` (`function`, optional) – callback for progress updates during obfuscation
**Returns:** `Promise<ObfuscationResult>`
> **Note:** When no Pro feature (`vmObfuscation` or `parseHtml`) is enabled, the Pro API is not needed, so `obfuscatePro` falls back to the basic (local) obfuscation API and no API request is made.
**Throws:** `ApiError` if:
- API token is invalid or expired
- API request fails
### Pro API with Specific Version
You can specify which obfuscator version to use via the `version` option:
```javascript
const result = await JavaScriptObfuscator.obfuscatePro(
sourceCode,
{
vmObfuscation: true
},
{
apiToken: 'your_javascript_obfuscator_pro_api_token',
version: '5.0.3' // Use specific version
}
);
```
### Pro API with Progress Updates
The API uses streaming mode to provide real-time progress updates during obfuscation:
```javascript
const result = await JavaScriptObfuscator.obfuscatePro(
sourceCode,
{
vmObfuscation: true
},
{
apiToken: 'your_javascript_obfuscator_pro_api_token'
},
(message) => {
console.log('Progress:', message);
// Output: "Validating request...", "Authenticating...", "Obfuscating...", etc.
}
);
```
### Checking for Pro Features
Use `ProApiClient.hasProFeatures()` to check if options require the Pro API:
```javascript
const { ProApiClient } = require('javascript-obfuscator');
const options = { vmObfuscation: true, compact: true };
if (ProApiClient.hasProFeatures(options)) {
// Use obfuscatePro() - requires API token
const result = await JavaScriptObfuscator.obfuscatePro(sourceCode, options, { apiToken });
} else {
// Use regular obfuscate() - no API token needed
const result = JavaScriptObfuscator.obfuscate(sourceCode, options);
}
```
Pro features include:
- `vmObfuscation: true` – VM-based bytecode obfuscation
- `parseHtml: true` – HTML parsing with inline JavaScript obfuscation
### Error Handling
```javascript
const { ApiError } = require('javascript-obfuscator');
try {
const result = await JavaScriptObfuscator.obfuscatePro(sourceCode, options, config);
} catch (error) {
if (error instanceof ApiError) {
console.error(`API Error (${error.statusCode}): ${error.message}`);
} else {
throw error;
}
}
```
### CLI Usage with Pro API
You can also use Pro API features directly from the CLI by providing your API token:
```sh
javascript-obfuscator input.js --pro-api-token YOUR_API_TOKEN --vm-obfuscation true -o output.js
```
With a specific obfuscator version:
```sh
javascript-obfuscator input.js --pro-api-token YOUR_API_TOKEN --pro-api-version 5.0.3 --vm-obfuscation true -o output.js
```
**CLI Options:**
- `--pro-api-token <string>` – Your API token from [obfuscator.io](https://obfuscator.io)
- `--pro-api-version <string>` – Obfuscator.io version to use (optional, defaults to latest)
The CLI automatically detects when Pro features (`vmObfuscation` or `parseHtml`) are enabled and routes the request through the Pro API.
### Large File Uploads
For files larger than ~4MB, the Pro API uses client-side uploads to Vercel Blob storage. To enable this feature, install the optional `@vercel/blob` package:
```sh
npm install @vercel/blob
```
Without this package, large file obfuscation will fail with an error message prompting you to install it.
---
## CLI usage
See [CLI options](#cli-options).
#### Obfuscate single file
Usage:
```sh
javascript-obfuscator input_file_name.js [options]
javascript-obfuscator input_file_name.js --output output_file_name.js [options]
javascript-obfuscator input_file_name.js --output output_folder_name [options]
javascript-obfuscator input_folder_name --output output_folder_name [options]
```
Obfuscation of single input file with `.js` extension.
If the destination path is not specified with the `--output` option, the obfuscated file will be saved into the input file directory, with `INPUT_FILE_NAME-obfuscated.js` name.
Some examples:
```sh
javascript-obfuscator samples/sample.js --compact true --self-defending false
// creates a new file samples/sample-obfuscated.js
javascript-obfuscator samples/sample.js --output output/output.js --compact true --self-defending false
// creates a new file output/output.js
```
#### Obfuscate directory recursively
Usage:
```sh
javascript-obfuscator ./dist [options]
// creates a new obfuscated files under `./dist` directory near the input files with `obfuscated` postfix
javascript-obfuscator ./dist --output ./dist/obfuscated [options]
// creates a folder structure with obfuscated files under `./dist/obfuscated` path
```
Obfuscation of all `.js` files under input directory. If this directory contains already obfuscated files with `-obfuscated` postfix - these files will ignored.
Obfuscated files will saved into the input directory under `INPUT_FILE_NAME-obfuscated.js` name.
## Conditional comments
You can disable and enable obfuscation for specific parts of the code by adding following comments:
* disable: `// javascript-obfuscator:disable` or `/* javascript-obfuscator:disable */`;
* enable: `// javascript-obfuscator:enable` or `/* javascript-obfuscator:enable */`.
Example:
```javascript
// input
var foo = 1;
// javascript-obfuscator:disable
var bar = 2;
// output
var _0xabc123 = 0x1;
var bar = 2;
```
Conditional comments affect only direct transformations of AST-tree nodes. All child transformations still will be applied to the AST-tree nodes.
For example:
* Obfuscation of the variable's name at its declaration is called direct transformation;
* Obfuscation of the variable's name beyond its declaration is called child transformation.
## Kind of variables
Kind of variables of inserted nodes will auto-detected, based on most prevailing kind of variables of source code.
## Conflicts of identifier names between different files
During obfuscation of the different files, the same names can be generated for the global identifiers between these files.
To prevent this set the unique prefix for all global identifiers for each obfuscated file with [`identifiersPrefix`](#identifiersprefix) option.
When using CLI this prefix will be added automatically.
## JavaScript Obfuscator Options
> :shield: **Looking for VM obfuscation?** Options like `vmObfuscation`, `parseHtml`, and every `vm*` option are Pro-only and require an API token from [obfuscator.io](https://obfuscator.io). Use them via the [`obfuscatePro()`](#shield-pro-api-methods-vm-obfuscation) method, or the `--pro-api-token` CLI flag — see [Pro API Methods](#shield-pro-api-methods-vm-obfuscation).
Following options are available for the JS Obfuscator:
#### options:
```javascript
{
compact: true,
controlFlowFlattening: false,
controlFlowFlatteningThreshold: 0.75,
deadCodeInjection: false,
deadCodeInjectionThreshold: 0.4,
debugProtection: false,
debugProtectionInterval: 0,
disableConsoleOutput: false,
domainLock: [],
domainLockRedirectUrl: 'about:blank',
forceTransformStrings: [],
identifierNamesCache: null,
identifierNamesGenerator: 'hexadecimal',
identifiersDictionary: [],
identifiersPrefix: '',
ignoreImports: false,
inputFileName: '',
log: false,
numbersToExpressions: false,
optionsPreset: 'default',
renameGlobals: false,
renameProperties: false,
renamePropertiesMode: 'safe',
reservedNames: [],
reservedStrings: [],
seed: 0,
selfDefending: false,
simplify: true,
sourceMap: false,
sourceMapBaseUrl: '',
sourceMapFileName: '',
sourceMapMode: 'separate',
sourceMapSourcesMode: 'sources-content',
splitStrings: false,
splitStringsChunkLength: 10,
stringArray: true,
stringArrayCallsTransform: true,
stringArrayCallsTransformThreshold: 0.5,
stringArrayEncoding: [],
stringArrayIndexesType: [
'hexadecimal-number'
],
stringArrayIndexShift: true,
stringArrayRotate: true,
stringArrayShuffle: true,
stringArrayWrappersCount: 1,
stringArrayWrappersChainedCalls: true,
stringArrayWrappersParametersMaxCount: 2,
stringArrayWrappersType: 'variable',
stringArrayThreshold: 0.75,
target: 'browser',
transformObjectKeys: false,
unicodeEscapeSequence: false
}
```
#### CLI options:
```sh
-v, --version
-h, --help
-o, --output
--compact <boolean>
--config <string>
--control-flow-flattening <boolean>
--control-flow-flattening-threshold <number>
--dead-code-injection <boolean>
--dead-code-injection-threshold <number>
--debug-protection <boolean>
--debug-protection-interval <number>
--disable-console-output <boolean>
--domain-lock '<list>' (comma separated)
--domain-lock-redirect-url <string>
--exclude '<list>' (comma separated)
--force-transform-strings '<list>' (comma separated)
--identifier-names-cache-path <string>
--identifier-names-generator <string> [dictionary, hexadecimal, mangled, mangled-shuffled]
--identifiers-dictionary '<list>' (comma separated)
--identifiers-prefix <string>
--random-identifiers-prefix <boolean>
--ignore-imports <boolean>
--log <boolean>
--numbers-to-expressions <boolean>
--options-preset <string> [default, low-obfuscation, medium-obfuscation, high-obfuscation]
--rename-globals <boolean>
--rename-properties <boolean>
--rename-properties-mode <string> [safe, unsafe]
--reserved-names '<list>' (comma separated)
--reserved-strings '<list>' (comma separated)
--seed <string|number>
--self-defending <boolean>
--simplify <boolean>
--source-map <boolean>
--source-map-base-url <string>
--source-map-file-name <string>
--source-map-mode <string> [inline, separate]
--source-map-sources-mode <string> [sources, sources-content]
--split-strings <boolean>
--split-strings-chunk-length <number>
--string-array <boolean>
--string-array-calls-transform <boolean>
--string-array-calls-transform-threshold <number>
--string-array-encoding '<list>' (comma separated) [none, base64, rc4]
--string-array-indexes-type '<list>' (comma separated) [hexadecimal-number, hexadecimal-numeric-string]
--string-array-index-shift <boolean>
--string-array-rotate <boolean>
--string-array-shuffle <boolean>
--string-array-wrappers-count <number>
--string-array-wrappers-chained-calls <boolean>
--string-array-wrappers-parameters-max-count <number>
--string-array-wrappers-type <string> [variable, function]
--string-array-threshold <number>
--target <string> [browser, browser-no-eval, node]
--browser-environment <string> [http, https]
--transform-object-keys <boolean>
--unicode-escape-sequence <boolean>
--pro-api-token <string>
--pro-api-version <string>
--vm-obfuscation <boolean>
--vm-obfuscation-threshold <number>
--vm-preprocess-identifiers <boolean>
--vm-dynamic-opcodes <boolean>
--vm-target-functions '<list>' (comma separated)
--vm-exclude-functions '<list>' (comma separated)
--vm-target-functions-mode <string> [root, comment]
--vm-force-compile-dynamic-code <boolean>
--vm-wrap-top-level-initializers <boolean>
--vm-opcode-shuffle <boolean>
--vm-bytecode-encoding <boolean>
--vm-bytecode-array-encoding <boolean>
--vm-bytecode-array-encoding-key <string>
--vm-bytecode-array-encoding-key-getter <string>
--vm-instruction-shuffle <boolean>
--vm-jumps-encoding <boolean>
--vm-decoy-opcodes <boolean>
--vm-dead-code-injection <boolean>
--vm-split-dispatcher <boolean>
--vm-macro-ops <boolean>
--vm-debug-protection <boolean>
--vm-self-defending <boolean>
--vm-runtime-opcode-derivation <boolean>
--vm-stateful-opcodes <boolean>
--vm-async-executor <boolean>
--vm-call-context-opcodes <boolean>
--vm-stack-encoding <boolean>
--vm-randomize-keys <boolean>
--vm-indirect-dispatch <boolean>
--vm-compact-dispatcher <boolean>
--vm-register-based <boolean>
--vm-string-array-bytecode-only <boolean>
--vm-domain-lock '<list>' (comma separated)
--vm-domain-lock-redirect-url <string>
--vm-bytecode-format <string> [binary, json]
--parse-html <boolean>
--strict-mode <boolean>
```
<!-- ##options-start## -->
### `compact`
Type: `boolean` Default: `true`
Compact code output on one line.
### `config`
Type: `string` Default: ``
Name of JS/JSON config file which contains obfuscator options. These will be overridden by options passed directly to CLI
### `controlFlowFlattening`
Type: `boolean` Default: `false`
##### :warning: This option greatly affects the performance up to 1.5x slower runtime speed. Use [`controlFlowFlatteningThreshold`](#controlflowflatteningthreshold) to set percentage of nodes that will affected by control flow flattening.
Enables code control flow flattening. Control flow flattening is a structure transformation of the source code that hinders program comprehension.
Example:
```ts
// input
(function(){
function foo () {
return function () {
var sum = 1 + 2;
console.log(1);
console.log(2);
console.log(3);
console.log(4);
console.log(5);
console.log(6);
}
}
foo()();
})();
// output
(function () {
function _0x3bfc5c() {
return function () {
var _0x3260a5 = {
'WtABe': '4|0|6|5|3|2|1',
'GokKo': function _0xf87260(_0x427a8e, _0x43354c) {
return _0x427a8e + _0x43354c;
}
};
var _0x1ad4d6 = _0x3260a5['WtABe']['split']('|'), _0x1a7b12 = 0x0;
while (!![]) {
switch (_0x1ad4d6[_0x1a7b12++]) {
case '0':
console['log'](0x1);
continue;
case '1':
console['log'](0x6);
continue;
case '2':
console['log'](0x5);
continue;
case '3':
console['log'](0x4);
continue;
case '4':
var _0x1f2f2f = _0x3260a5['GokKo'](0x1, 0x2);
continue;
case '5':
console['log'](0x3);
continue;
case '6':
console['log'](0x2);
continue;
}
break;
}
};
}
_0x3bfc5c()();
}());
```
### `controlFlowFlatteningThreshold`
Type: `number` Default: `0.75` Min: `0` Max: `1`
The probability that the [`controlFlowFlattening`](#controlflowflattening) transformation will be applied to any given node.
This setting is especially useful for large code size because large amounts of control flow transformations can slow down your code and increase code size.
`controlFlowFlatteningThreshold: 0` equals to `controlFlowFlattening: false`.
### `deadCodeInjection`
Type: `boolean` Default: `false`
##### :warning: Dramatically increases size of obfuscated code (up to 200%), use only if size of obfuscated code doesn't matter. Use [`deadCodeInjectionThreshold`](#deadcodeinjectionthreshold) to set percentage of nodes that will affected by dead code injection.
##### :warning: This option forcibly enables `stringArray` option.
With this option, random blocks of dead code will be added to the obfuscated code.
Example:
```ts
// input
(function(){
if (true) {
var foo = function () {
console.log('abc');
};
var bar = function () {
console.log('def');
};
var baz = function () {
console.log('ghi');
};
var bark = function () {
console.log('jkl');
};
var hawk = function () {
console.log('mno');
};
foo();
bar();
baz();
bark();
hawk();
}
})();
// output
var _0x37b8 = [
'YBCtz',
'GlrkA',
'urPbb',
'abc',
'NMIhC',
'yZgAj',
'zrAId',
'EtyJA',
'log',
'mno',
'jkl',
'def',
'Quzya',
'IWbBa',
'ghi'
];
function _0x43a7(_0x12cf56, _0x587376) {
_0x43a7 = function (_0x2f87a8, _0x47eac2) {
_0x2f87a8 = _0x2f87a8 - (0x16a7 * 0x1 + 0x5 * 0x151 + -0x1c92);
var _0x341e03 = _0x37b8[_0x2f87a8];
return _0x341e03;
};
return _0x43a7(_0x12cf56, _0x587376);
}
(function () {
if (!![]) {
var _0xbbe28f = function () {
var _0x2fc85f = _0x43a7;
if (_0x2fc85f(0xaf) === _0x2fc85f(0xae)) {
_0x1dd94f[_0x2fc85f(0xb2)](_0x2fc85f(0xb5));
} else {
console[_0x2fc85f(0xb2)](_0x2fc85f(0xad));
}
};
var _0x5e46bc = function () {
var _0x15b472 = _0x43a7;
if (_0x15b472(0xb6) !== _0x15b472(0xaa)) {
console[_0x15b472(0xb2)](_0x15b472(0xb5));
} else {
_0x47eac2[_0x15b472(0xb2)](_0x15b472(0xad));
}
};
var _0x3669e8 = function () {
var _0x47a442 = _0x43a7;
if (_0x47a442(0xb7) !== _0x47a442(0xb0)) {
console[_0x47a442(0xb2)](_0x47a442(0xb8));
} else {
_0x24e0bf[_0x47a442(0xb2)](_0x47a442(0xb3));
}
};
var _0x28b05a = function () {
var _0x497902 = _0x43a7;
if (_0x497902(0xb1) === _0x497902(0xb1)) {
console[_0x497902(0xb2)](_0x497902(0xb4));
} else {
_0x59c9c6[_0x497902(0xb2)](_0x497902(0xb4));
}
};
var _0x402a54 = function () {
var _0x1906b7 = _0x43a7;
if (_0x1906b7(0xab) === _0x1906b7(0xac)) {
_0xb89cd0[_0x1906b7(0xb2)](_0x1906b7(0xb8));
} else {
console[_0x1906b7(0xb2)](_0x1906b7(0xb3));
}
};
_0xbbe28f();
_0x5e46bc();
_0x3669e8();
_0x28b05a();
_0x402a54();
}
}());
```
### `deadCodeInjectionThreshold`
Type: `number` Default: `0.4` Min: `0` Max: `1`
Allows to set percentage of nodes that will affected by `deadCodeInjection`.
### `debugProtection`
Type: `boolean` Default: `false`
##### :warning: Can freeze your browser if you open the Developer Tools.
This option makes it almost impossible to use the `debugger` function of the Developer Tools (both on WebKit-based and Mozilla Firefox).
### `debugProtectionInterval`
Type: `number` Default: `0`
##### :warning: Can freeze your browser! Use at own risk.
If set, an interval in milliseconds is used to force the debug mode on the Console tab, making it harder to use other features of the Developer Tools. Works if [`debugProtection`](#debugprotection) is enabled. Recommended value is between `2000` and `4000` milliseconds.
### `disableConsoleOutput`
Type: `boolean` Default: `false`
##### :warning: This option disables `console` calls globally for all scripts
Disables the use of `console.log`, `console.info`, `console.error`, `console.warn`, `console.debug`, `console.exception` and `console.trace` by replacing them with empty functions. This makes the use of the debugger harder.
### `domainLock`
Type: `string[]` Default: `[]`
##### :warning: This option does not work with `target: 'node'`
Allows to run the obfuscated source code only on specific domains and/or sub-domains. This makes really hard for someone to just copy and paste your source code and run it elsewhere.
If the source code isn't run on the domains specified by this option, the browser will be redirected to a passed to the [`domainLockRedirectUrl`](#domainlockredirecturl) option URL.
##### Multiple domains and sub-domains
It's possible to lock your code to more than one domain or sub-domain. For instance, to lock it so the code only runs on **www.example.com** add `www.example.com`. To make it work on the root domain including any sub-domains (`example.com`, `sub.example.com`), use `.example.com`.
### `domainLockRedirectUrl`
Type: `string` Default: `about:blank`
##### :warning: This option does not work with `target: 'node'`
Allows the browser to be redirected to a passed URL if the source code isn't run on the domains specified by [`domainLock`](#domainlock)
### `exclude`
Type: `string[]` Default: `[]`
A file names or globs which indicates files to exclude from obfuscation.
### `forceTransformStrings`
Type: `string[]` Default: `[]`
Enables force transformation of string literals, which being matched by passed RegExp patterns.
##### :warning: This option affects only strings that shouldn't be transformed by [`stringArrayThreshold`](#stringarraythreshold) (or possible other thresholds in the future)
The option has a priority over `reservedStrings` option but hasn't a priority over `conditional comments`.
Example:
```ts
{
forceTransformStrings: [
'some-important-value',
'some-string_\d'
]
}
```
### `identifierNamesCache`
Type: `Object | null` Default: `null`
The main goal for this option is the ability to use the same identifier names during obfuscation of multiple sources/files.
Currently the two types of the identifiers are supported:
- Global identifiers:
* All global identifiers will be written to the cache;
* All matched **undeclared** global identifiers will be replaced by the values from the cache.
- Property identifiers, only when `renameProperties` option is enabled:
* All property identifiers will be written to the cache;
* All matched property identifiers will be replaced by the values from the cache.
#### Node.js API
If a `null` value is passed, completely disables the cache.
If an empty object (`{}`) is passed, enables the writing identifier names to the cache-object (`TIdentifierNamesCache` type). This cache-object will be accessed through the `getIdentifierNamesCache` method call of `ObfuscationResult` object.
The resulting cache-object can be next used as `identifierNamesGenerator` option value for using these names during obfuscation of all matched identifier names of next sources.
Example:
```ts
const source1ObfuscationResult = JavaScriptObfuscator.obfuscate(
`
function foo(arg) {
console.log(arg)
}
function bar() {
var bark = 2;
}
`,
{
compact: false,
identifierNamesCache: {},
renameGlobals: true
}
)
console.log(source1ObfuscationResult.getIdentifierNamesCache());
/*
{
globalIdentifiers: {
foo: '_0x5de86d',
bar: '_0x2a943b'
}
}
*/
const source2ObfuscationResult = JavaScriptObfuscator.obfuscate(
`
// Expecting that these global functions are defined in another obfuscated file
foo(1);
bar();
// Expecting that this global function is defined in third-party package
baz();
`,
{
compact: false,
identifierNamesCache: source1ObfuscationResult.getIdentifierNamesCache(),
renameGlobals: true
}
)
console.log(source2ObfuscationResult.getObfuscatedCode());
/*
_0x5de86d(0x1);
_0x2a943b();
baz();
*/
```
#### CLI
CLI has a different option `--identifier-names-cache-path` that allows defining a path to the existing `.json` file that will be used to read and write identifier names cache.
If a path to the empty file will be passed - identifier names cache will be written to that file.
This file with existing cache can be used again as `--identifier-names-cache-path` option value for using these names during obfuscation of all matched identifier names of the next files.
### `identifierNamesGenerator`
Type: `string` Default: `hexadecimal`
Sets identifier names generator.
Available values:
* `dictionary`: identifier names from [`identifiersDictionary`](#identifiersdictionary) list
* `hexadecimal`: identifier names like `_0xabc123`
* `mangled`: short identifier names like `a`, `b`, `c`
* `mangled-shuffled`: same as `mangled` but with shuffled alphabet
### `identifiersDictionary`
Type: `string[]` Default: `[]`
Sets identifiers dictionary for [`identifierNamesGenerator`](#identifiernamesgenerator): `dictionary` option. Each identifier from the dictionary will be used in a few variants with a different casing of each character. Thus, the number of identifiers in the dictionary should depend on the identifiers amount at original source code.
### `identifiersPrefix`
Type: `string` Default: `''`
Sets prefix for all global identifiers.
Use this option when you want to obfuscate multiple files. This option helps to avoid conflicts between global identifiers of these files. Prefix should be different for every file.
### `ignoreImports`
Type: `boolean` Default: `false`
Prevents obfuscation of `require` imports. Could be helpful in some cases when for some reason runtime environment requires these imports with static strings only.
### `inputFileName`
Type: `string` Default: `''`
Allows to set name of the input file with source code. This name will be used internally for source map generation.
Required when using NodeJS API and `sourceMapSourcesMode` option has `sources` value`.
### `log`
Type: `boolean` Default: `false`
Enables logging of the information to the console.
### `numbersToExpressions`
Type: `boolean` Default: `false`
Enables numbers conversion to expressions
Example:
```ts
// input
const foo = 1234;
// output
const foo=-0xd93+-0x10b4+0x41*0x67+0x84e*0x3+-0xff8;
```
### `optionsPreset`
Type: `string` Default: `default`
Allows to set [options preset](#preset-options).
Available values:
* `default`;
* `low-obfuscation`;
* `medium-obfuscation`;
* `high-obfuscation`.
All addition options will be merged with selected options preset.
### `renameGlobals`
Type: `boolean` Default: `false`
##### :warning: this option can break your code. Enable it only if you know what it does!
Enables obfuscation of global variable and function names **with declaration**.
### `renameProperties`
Type: `boolean` Default: `false`
##### :warning: this option **MAY** break your code. Enable it only if you know what it does!
Enables renaming of property names. All built-in DOM properties and properties in core JavaScript classes will be ignored.
To switch between `safe` and `unsafe` modes of this option use [`renamePropertiesMode`](#renamepropertiesmode) option.
To set format of renamed property names use [`identifierNamesGenerator`](#identifiernamesgenerator) option.
To control which properties will be renamed use [`reservedNames`](#reservednames) option.
Example:
```ts
// input
(function () {
const foo = {
prop1: 1,
prop2: 2,
calc: function () {
return this.prop1 + this.prop2;
}
};
console.log(foo.calc());
})();
// output
(function () {
const _0x46529b = {
'_0x10cec7': 0x1,
'_0xc1c0ca': 0x2,
'_0x4b961d': function () {
return this['_0x10cec7'] + this['_0xc1c0ca'];
}
};
console['log'](_0x46529b['_0x4b961d']());
}());
```
### `renamePropertiesMode`
Type: `string` Default: `safe`
##### :warning: Even in `safe` mode, [`renameProperties`](#renameproperties) option **MAY** break your code.
Specifies `renameProperties` option mode:
* `safe` - default behaviour after `2.11.0` release. Trying to rename properties in a more safe way to prevent runtime errors. With this mode some properties will be excluded from renaming.
* `unsafe` - default behaviour before `2.11.0` release. Renames properties in an unsafe way without any restrictions.
If one file is using properties from other file, use [`identifierNamesCache`](#identifiernamescache) option to keep the same property names between these files.
### `reservedNames`
Type: `string[]` Default: `[]`
Disables obfuscation and generation of identifiers, which being matched by passed RegExp patterns.
Example:
```ts
{
reservedNames: [
'^someVariable',
'functionParameter_\d'
]
}
```
### `reservedStrings`
Type: `string[]` Default: `[]`
Disables transformation of string literals, which being matched by passed RegExp patterns.
Example:
```ts
{
reservedStrings: [
'react-native',
'\.\/src\/test',
'some-string_\d'
]
}
```
### `seed`
Type: `string|number` Default: `0`
This option sets seed for random generator. This is useful for creating repeatable results.
If seed is `0` - random generator will work without seed.
### `selfDefending`
Type: `boolean` Default: `false`
##### :warning: Don't change obfuscated code in any way after obfuscation with this option, because any change like uglifying of code can trigger self defending and code wont work anymore!
##### :warning: This option forcibly sets `compact` value to `true`
This option makes the output code resilient against formatting and variable renaming. If one tries to use a JavaScript beautifier on the obfuscated code, the code won't work anymore, making it harder to understand and modify it.
### `simplify`
Type: `boolean` Default: `true`
Enables additional code obfuscation through simplification.
##### :warning: in future releases obfuscation of `boolean` literals (`true` => `!![]`) will be moved under this option.
Example:
```ts
// input
if (condition1) {
const foo = 1;
const bar = 2;
console.log(foo);
return bar;
} else if (condition2) {
console.log(1);
console.log(2);
console.log(3);
return 4;
} else {
return 5;
}
// output
if (condition1) {
const foo = 0x1, bar = 0x2;
return console['log'](foo), bar;
} else
return condition2 ? (console['log'](0x1), console['log'](0x2), console['log'](0x3), 0x4) : 0x5;
```
### `sourceMap`
Type: `boolean` Default: `false`
Enables source map generation for obfuscated code.
Source maps can be useful to help you debug your obfuscated JavaScript source code. If you want or need to debug in production, you can upload the separate source map file to a secret location and then point your browser there.
### `sourceMapBaseUrl`
Type: `string` Default: ``
Sets base url to the source map import url when [`sourceMapMode: 'separate'`](#sourcemapmode).
CLI example:
```
javascript-obfuscator input.js --output out.js --source-map true --source-map-base-url 'http://localhost:9000'
```
Result:
```
//# sourceMappingURL=http://localhost:9000/out.js.map
```
### `sourceMapFileName`
Type: `string` Default: ``
Sets file name for output source map when `sourceMapMode: 'separate'`.
CLI example:
```
javascript-obfuscator input.js --output out.js --source-map true --source-map-base-url 'http://localhost:9000' --source-map-file-name example
```
Result:
```
//# sourceMappingURL=http://localhost:9000/example.js.map
```
### `sourceMapMode`
Type: `string` Default: `separate`
Specifies source map generation mode:
* `inline` - add source map at the end of each .js files;
* `separate` - generates corresponding '.map' file with source map. In case you run obfuscator through CLI - adds link to source map file to the end of file with obfuscated code `//# sourceMappingUrl=file.js.map`.
### `sourceMapSourcesMode`
Type: `string` Default: `sources-content`
Allows to control `sources` and `sourcesContent` fields of the source map:
* `sources-content` - adds dummy `sources` field, adds `sourcesContent` field with the original source code;
* `sources` - adds `sources` field with a valid source description, does not add `sourcesContent` field. When using NodeJS API it's required to define `inputFileName` option that will be used as `sources` field value.
### `splitStrings`
Type: `boolean` Default: `false`
Splits literal strings into chunks with length of [`splitStringsChunkLength`](#splitstringschunklength) option value.
Example:
```ts
// input
(function(){
var test = 'abcdefg';
})();
// output
(function(){
var _0x5a21 = 'ab' + 'cd' + 'ef' + 'g';
})();
```
### `splitStringsChunkLength`
Type: `number` Default: `10`
Sets chunk length of [`splitStrings`](#splitstrings) option.
### `stringArray`
Type: `boolean` Default: `true`
Removes string literals and place them in a special array. For instance, the string `"Hello World"` in `var m = "Hello World";` will be replaced with something like `var m = _0x12c456[0x1];`
### `stringArrayCallsTransform`
Type: `boolean` Default: `false`
##### :warning: [`stringArray`](#stringarray) option must be enabled
Enables the transformation of calls to the [`stringArray`](#stringarray). All arguments of these calls may be extracted to a different object depending on [`stringArrayCallsTransformThreshold`](#stringarraycallstransformthreshold) value.
So it makes it even harder to automatically find calls to the string array.
Example:
```
function foo() {
var k = {
c: 0x2f2,
d: '0x396',
e: '0x397',
f: '0x39a',
g: '0x39d',
h: 0x398,
l: 0x394,
m: '0x39b',
n: '0x39f',
o: 0x395,
p: 0x395,
q: 0x399,
r: '0x399'
};
var c = i(k.d, k.e);
var d = i(k.f, k.g);
var e = i(k.h, k.l);
var f = i(k.m, k.n);
function i(c, d) {
return b(c - k.c, d);
}
var g = i(k.o, k.p);
var h = i(k.q, k.r);
}
function j(c, d) {
var l = { c: 0x14b };
return b(c - -l.c, d);
}
console[j(-'0xa6', -'0xa6')](foo());
function b(c, d) {
var e = a();
b = function (f, g) {
f = f - 0xa3;
var h = e[f];
return h;
};
return b(c, d);
}
function a() {
var m = [
'string5',
'string1',
'log',
'string3',
'string6',
'string2',
'string4'
];
a = function () {
return m;
};
return a();
}
```
### `stringArrayCallsTransformThreshold`
Type: `number` Default: `0.5`
##### :warning: [`stringArray`](#stringarray) and [`stringArrayCallsTransformThreshold`](#stringarraycallstransformthreshold) options must be enabled
You can use this setting to adjust the probability (from 0 to 1) that calls to the string array will be transformed.
### `stringArrayEncoding`
Type: `string[]` Default: `[]`
##### :warning: `stringArray` option must be enabled
This option can slow down your script.
Encode all string literals of the [`stringArray`](#stringarray) using `base64` or `rc4` and inserts a special code that used to decode it back at runtime.
Each `stringArray` value will be encoded by the randomly picked encoding from the passed list. This makes possible to use multiple encodings.
Available values:
* `'none'` (`boolean`): doesn't encode `stringArray` value
* `'base64'` (`string`): encodes `stringArray` value using `base64`
* `'rc4'` (`string`): encodes `stringArray` value using `rc4`. **About 30-50% slower than `base64`, but harder to get initial values.** It's recommended to disable [`unicodeEscapeSequence`](#unicodeescapesequence) option when using `rc4` encoding to prevent very large size of obfuscated code.
For example with the following option values some `stringArray` value won't be encoded, and some values will be encoded with `base64` and `rc4` encoding:
```ts
stringArrayEncoding: [
'none',
'base64',
'rc4'
]
```
### `stringArrayIndexesType`
Type: `string[]` Default: `['hexadecimal-number']`
##### :warning: `stringArray` option must be enabled
Allows to control the type of string array call indexes.
Each `stringArray` call index will be transformed by the randomly picked type from the passed list. This makes possible to use multiple types.
Available values:
* `'hexadecimal-number'` (`default`): transforms string array call indexes as hexadecimal numbers
* `'hexadecimal-numeric-string'`: transforms string array call indexes as hexadecimal numeric string
Before `2.9.0` release `javascript-obfuscator` transformed all string array call indexes with `hexadecimal-numeric-string` type. This makes some manual deobfuscation slightly harder but it allows easy detection of these calls by automatic deobfuscators.
The new `hexadecimal-number` type approaches to make harder auto-detect of string array call patterns in the code.
More types will be added in the future.
### `stringArrayIndexShift`
Type: `boolean` Default: `true`
##### :warning: `stringArray` option must be enabled
Enables additional index shift for all string array calls
### `stringArrayRotate`
Type: `boolean` Default: `true`
##### :warning: [`stringArray`](#stringarray) must be enabled
Shift the `stringArray` array by a fixed and random (generated at the code obfuscation) places. This makes it harder to match the order of the removed strings to their original place.
### `stringArrayShuffle`
Type: `boolean` Default: `true`
##### :warning: [`stringArray`](#stringarray) must be enabled
Randomly shuffles the `stringArray` array items.
### `stringArrayWrappersCount`
Type: `number` Default: `1`
##### :warning: [`stringArray`](#stringarray) option must be enabled
Sets the count of wrappers for the `string array` inside each root or function scope.
The actual count of wrappers inside each scope is limited by a count of `literal` nodes within this scope.
Example:
```ts
// Input
const foo = 'foo';
const bar = 'bar';
function test () {
const baz = 'baz';
const bark = 'bark';
const hawk = 'hawk';
}
const eagle = 'eagle';
// Output, stringArrayWrappersCount: 5
const _0x3f6c = [
'bark',
'bar',
'foo',
'eagle',
'hawk',
'baz'
];
const _0x48f96e = _0x2e13;
const _0x4dfed8 = _0x2e13;
const _0x55e970 = _0x2e13;
function _0x2e13(_0x33c4f5, _0x3f6c62) {
_0x2e13 = function (_0x2e1388, _0x60b1e) {
_0x2e1388 = _0x2e1388 - 0xe2;
let _0x53d475 = _0x3f6c[_0x2e1388];
return _0x53d475;
};
return _0x2e13(_0x33c4f5, _0x3f6c62);
}
const foo = _0x48f96e(0xe4);
const bar = _0x4dfed8(0xe3);
function test() {
const _0x1c262f = _0x2e13;
const _0x54d7a4 = _0x2e13;
const _0x5142fe = _0x2e13;
const _0x1392b0 = _0x1c262f(0xe7);
const _0x201a58 = _0x1c262f(0xe2);
const _0xd3a7fb = _0x1c262f(0xe6);
}
const eagle = _0x48f96e(0xe5);
```
### `stringArrayWrappersChainedCalls`
Type: `boolean` Default: `true`
##### :warning: [`stringArray`](#stringarray) and [`stringArrayWrappersCount`](#stringarraywrapperscount) options must be enabled
Enables the chained calls between `string array` wrappers.
Example:
```ts
// Input
const foo = 'foo';
const bar = 'bar';
function test () {
const baz = 'baz';
const bark = 'bark';
function test1() {
const hawk = 'hawk';
const eagle = 'eagle';
}
}
// Output, stringArrayWrappersCount: 5, stringArrayWrappersChainedCalls: true
const _0x40c2 = [
'bar',
'bark',
'hawk',
'eagle',
'foo',
'baz'
];
const _0x31c087 = _0x3280;
const _0x31759a = _0x3280;
function _0x3280(_0x1f52ee, _0x40c2a2) {
_0x3280 = function (_0x3280a4, _0xf07b02) {
_0x3280a4 = _0x3280a4 - 0x1c4;
let _0x57a182 = _0x40c2[_0x3280a4];
return _0x57a182;
};
return _0x3280(_0x1f52ee, _0x40c2a2);
}
const foo = _0x31c087(0x1c8);
const bar = _0x31c087(0x1c4);
function test() {
const _0x848719 = _0x31759a;
const _0x2693bf = _0x31c087;
const _0x2c08e8 = _0x848719(0x1c9);
const _0x359365 = _0x2693bf(0x1c5);
function _0x175e90() {
const _0x310023 = _0x848719;
const _0x2302ef = _0x2693bf;
const _0x237437 = _0x310023(0x1c6);
const _0x56145c = _0x310023(0x1c7);
}
}
```
### `stringArrayWrappersParametersMaxCount`
Type: `number` Default: `2`
##### :warning: [`stringArray`](#stringarray) option must be enabled
##### :warning: Currently this option affects only wrappers added by [`stringArrayWrappersType`](#stringarraywrapperstype) `function` option value
Allows to control the maximum number of string array wrappers parameters.
Default and minimum value is `2`. Recommended value between `2` and `5`.
### `stringArrayWrappersType`
Type: `string` Default: `variable`
##### :warning: [`stringArray`](#stringarray) and [`stringArrayWrappersCount`](#stringarraywrapperscount) options must be enabled
Allows to select a type of the wrappers that are appending by the `stringArrayWrappersCount` option.
Available values:
* `'variable'`: appends variable wrappers at the top of each scope. Fast performance.
* `'function'`: appends function wrappers at random positions inside each scope. Slower performance than with `variable` but provides more strict obfuscation.
Highly recommended to use `function` wrappers for higher obfuscation when a performance loss doesn't have a high impact on an obfuscated application.
Example of the `'function'` option value:
```ts
// input
const foo = 'foo';
function test () {
const bar = 'bar';
console.log(foo, bar);
}
test();
// output
const a = [
'log',
'bar',
'foo'
];
const foo = d(0x567, 0x568);
function b(c, d) {
b = function (e, f) {
e = e - 0x185;
let g = a[e];
return g;
};
return b(c, d);
}
function test() {
const c = e(0x51c, 0x51b);
function e (c, g) {
return b(c - 0x396, g);
}
console[f(0x51b, 0x51d)](foo, c);
function f (c, g) {
return b(c - 0x396, g);
}
}
function d (c, g) {
return b(g - 0x3e1, c);
}
test();
```
### `stringArrayThreshold`
Type: `number` Default: `0.8` Min: `0` Max: `1`
##### :warning: [`stringArray`](#stringarray) option must be enabled
You can use this setting to adjust the probability (from 0 to 1) that a string literal will be inserted into the `stringArray`.
This setting is especially useful for large code size because it repeatedly calls to the `string array` and can slow down your code.
`stringArrayThreshold: 0` equals to `stringArray: false`.
### `target`
Type: `string` Default: `browser`
Allows to set target environment for obfuscated code.
Available values:
* `browser`;
* `browser-no-eval`;
* `node`.
Currently output code for `browser` and `node` targets is identical, but some browser-specific options are not allowed to use with `node` target.
Output code for `browser-no-eval` target is not using `eval`.
### `transformObjectKeys`
Type: `boolean` Default: `false`
Enables transformation of object keys.
Example:
```ts
// input
(function(){
var object = {
foo: 'test1',
bar: {
baz: 'test2'
}
};
})();
// output
var _0x4735 = [
'foo',
'baz',
'bar',
'test1',
'test2'
];
function _0x390c(_0x33d6b6, _0x4735f4) {
_0x390c = function (_0x390c37, _0x1eed85) {
_0x390c37 = _0x390c37 - 0x198;
var _0x2275f8 = _0x4735[_0x390c37];
return _0x2275f8;
};
return _0x390c(_0x33d6b6, _0x4735f4);
}
(function () {
var _0x17d1b7 = _0x390c;
var _0xc9b6bb = {};
_0xc9b6bb[_0x17d1b7(0x199)] = _0x17d1b7(0x19c);
var _0x3d959a = {};
_0x3d959a[_0x17d1b7(0x198)] = _0x17d1b7(0x19b);
_0x3d959a[_0x17d1b7(0x19a)] = _0xc9b6bb;
var _0x41fd86 = _0x3d959a;
}());
```
### `unicodeEscapeSequence`
Type: `boolean` Default: `false`
Allows to enable/disable string conversion to unicode escape sequence.
Unicode escape sequence increases code size greatly and strings easily can be reverted to their original view. Recommended to enable this option only for small source code.
## Preset Options
### High obfuscation, low performance
The performance will be much slower than without obfuscation
```javascript
{
compact: true,
controlFlowFlattening: true,
controlFlowFlatteningThreshold: 1,
deadCodeInjection: true,
deadCodeInjectionThreshold: 1,
debugProtection: true,
debugProtectionInterval: 4000,
disableConsoleOutput: true,
identifierNamesGenerator: 'hexadecimal',
log: false,
numbersToExpressions: true,
renameGlobals: false,
selfDefending: true,
simplify: true,
splitStrings: true,
splitStringsChunkLength: 5,
stringArray: true,
stringArrayCallsTransform: true,
stringArrayEncoding: ['rc4'],
stringArrayIndexShift: true,
stringArrayRotate: true,
stringArrayShuffle: true,
stringArrayWrappersCount: 5,
stringArrayWrappersChainedCalls: true,
stringArrayWrappersParametersMaxCount: 5,
stringArrayWrappersType: 'function',
stringArrayThreshold: 1,
transformObjectKeys: true,
unicodeEscapeSequence: false
}
```
### Medium obfuscation, optimal performance
The performance will be slower than without obfuscation
```javascript
{
compact: true,
controlFlowFlattening: true,
controlFlowFlatteningThreshold: 0.75,
deadCodeInjection: true,
deadCodeInjectionThreshold: 0.4,
debugProtection: false,
debugProtectionInterval: 0,
disableConsoleOutput: true,
identifierNamesGenerator: 'hexadecimal',
log: false,
numbersToExpressions: true,
renameGlobals: false,
selfDefending: true,
simplify: true,
splitStrings: true,
splitStringsChunkLength: 10,
stringArray: true,
stringArrayCallsTransform: true,
stringArrayCallsTransformThreshold: 0.75,
stringArrayEncoding: ['base64'],
stringArrayIndexShift: true,
stringArrayRotate: true,
stringArrayShuffle: true,
stringArrayWrappersCount: 2,
stringArrayWrappersChainedCalls: true,
stringArrayWrappersParametersMaxCount: 4,
stringArrayWrappersType: 'function',
stringArrayThreshold: 0.75,
transformObjectKeys: true,
unicodeEscapeSequence: false
}
```
### Low obfuscation, High performance
The performance will be at a relatively normal level
```javascript
{
compact: true,
controlFlowFlattening: false,
deadCodeInjection: false,
debugProtection: false,
debugProtectionInterval: 0,
disableConsoleOutput: true,
identifierNamesGenerator: 'hexadecimal',
log: false,
numbersToExpressions: false,
renameGlobals: false,
selfDefending: true,
simplify: true,
splitStrings: false,
stringArray: true,
stringArrayCallsTransform: false,
stringArrayEncoding: [],
stringArrayIndexShift: true,
stringArrayRotate: true,
stringArrayShuffle: true,
stringArrayWrappersCount: 1,
stringArrayWrappersChainedCalls: true,
stringArrayWrappersParametersMaxCount: 2,
stringArrayWrappersType: 'variable',
stringArrayThreshold: 0.75,
unicodeEscapeSequence: false
}
```
### Default preset, High performance
```javascript
{
compact: true,
controlFlowFlattening: false,
deadCodeInjection: false,
debugProtection: false,
debugProtectionInterval: 0,
disableConsoleOutput: false,
identifierNamesGenerator: 'hexadecimal',
log: false,
numbersToExpressions: false,
renameGlobals: false,
selfDefending: false,
simplify: true,
splitStrings: false,
stringArray: true,
stringArrayCallsTransform: false,
stringArrayCallsTransformThreshold: 0.5,
stringArrayEncoding: [],
stringArrayIndexShift: true,
stringArrayRotate: true,
stringArrayShuffle: true,
stringArrayWrappersCount: 1,
stringArrayWrappersChainedCalls: true,
stringArrayWrappersParametersMaxCount: 2,
stringArrayWrappersType: 'variable',
stringArrayThreshold: 0.75,
unicodeEscapeSequence: false
}
```
<!-- ##options-end## -->
## Obfuscator.io Pro Options
> :warning: **The following VM obfuscation/Pro options are available only via the [Obfuscator.io Pro API](https://obfuscator.io/).**
>
> To use these options, you need a Pro API token from [obfuscator.io](https://obfuscator.io) and must call the `obfuscatePro()` method instead of `obfuscate()`. See the [Pro API Methods](#shield-pro-api-methods-vm-obfuscation) section for details.
### `vmObfuscation`
Type: `boolean` Default: `false`
Enables VM-based bytecode obfuscation. When enabled, JavaScript functions are compiled into custom bytecode that runs on an embedded virtual machine. This provides the highest level of protection as the original code logic is completely transformed.
**Example:**
Your readable code like `return qty * price` becomes a list of numbers like `[0x15,0x03,0x17,...]` that only the embedded VM interpreter can execute. The original logic is no longer visible as JavaScript.
### `vmTargetFunctions`
Type: `string[]` Default: `[]`
Specify exactly which root-level functions should get VM protection by name.
**Example:**
```javascript
{
vmObfuscation: true,
vmTargetFunctions: ['someFunctionName']
}
```
**Result:** Only these three functions get VM-protected. Everything else stays as regular (but still obfuscated) JavaScript. Perfect for protecting sensitive license checks or authentication logic while keeping the rest of your code lean.
### `vmExcludeFunctions`
Type: `string[]` Default: `[]`
Specify root-level functions that should never get VM protection. Takes precedence over other settings.
**Example:**
```javascript
{
vmObfuscation: true,
vmExcludeFunctions: ['someFunctionName']
}
```
**When to use:** Performance-critical root-level functions (animation loops, real-time data processing) can be excluded to avoid VM overhead while still protecting everything else.
### `vmTargetFunctionsMode`
Type: `string` Default: `root`
Controls how functions/methods are selected for VM obfuscation.
| Mode | Description |
|------|------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| `root` | Default behavior. Only root-level functions are considered for VM obfuscation. Uses `vmTargetFunctions` allow-list and `vmExcludeFunctions` deny-list to filter. |
| `comment` | Only functions/methods decorated with `/* javascript-obfuscator:vm */` comment are VM-obfuscated. Works with functions/methods at **any nesting level**. |
**Example - Comment mode:**
```javascript
// Source code
function regularFunction() {
return 'not virtualized';
}
/* javascript-obfuscator:vm */
function sensitiveFunction() {
return 'this will be VM-protected';
}
function outer() {
/* javascript-obfuscator:vm */
function nestedSensitive() {
return 'nested but still VM-protected';
}
return nestedSensitive();
}
```
```javascript
// Obfuscator options
{
vmObfuscation: true,
vmTargetFunctionsMode: 'comment'
}
```
**When to use:** When you need surgical control over exactly which functions get VM protection, especially nested functions that contain sensitive logic. Unlike `vmTargetFunctions` which only works with root-level named functions, comment mode lets you protect any function anywhere in your code.
### `vmForceCompileDynamicCode`
Type: `boolean` Default: `false`
Controls what VM obfuscation does with a function that contains a direct `eval`, `new Function(...)`, or `Function(...)` call.
By default, such a function (and every function defined inside it) is skipped from VM bytecoding and a `VMDynamicCodeSkipped` warning is reported on `result.getWarnings()`. This is because the runtime-built source may reference identifiers from the surrounding scope chain — identifiers that the obfuscator has renamed.
When set to `true`, the function is bytecoded anyway and the `VMDynamicCodeSkipped` warning is no longer emitted.
The separate `DynamicCodeRenameRisk` warning continues to fire regardless of this option, because the rename risk it describes is independent of the VM skip — turning this option on does not make the underlying pattern any safer.
```javascript
// Source code
function loadConfig(src) {
return eval(src);
}
loadConfig('1 + 2');
```
```javascript
// Options
{
vmObfuscation: true,
vmForceCompileDynamicCode: true
}
```
With the option off (default), `loadConfig` is left as plain JavaScript. With the option on, `loadConfig` is compiled to VM bytecode like any other function. Use this when you have audited the call site and know the runtime-built code does not depend on closure-renamed identifiers.
### `vmWrapTopLevelInitializers`
Type: `boolean` Default: `false`
Wraps some top-level variable initializers in IIFEs (Immediately Invoked Function Expressions) so they can be VM-obfuscated.
**What it does:**
Without this option, top-level constants and variables remain visible in the output:
```javascript
// Input
const MY_STRING = "my-string";
// Output (without vmWrapTopLevelInitializers)
const MY_STRING = "my-string"; // String is visible!
```
With this option enabled, the initializer is wrapped in an IIFE that gets VM-obfuscated:
```javascript
// Input
const MY_STRING = "my-string";
// Output (with vmWrapTopLevelInitializers: true)
const MY_STRING = (() => { return /* VM bytecode call */ })(); // String hidden in bytecode
```
**Note:** This option only works when `vmTargetFunctionsMode` is `'root'` (the default).
### `vmDynamicOpcodes`
Type: `boolean` Default: `false`
Makes the VM interpreter smaller and unique for each build.
**What it does:**
1. **Filters unused instructions** - If your code doesn't use classes, class-related instructions are removed entirely
2. **Randomizes structure** - The order of instruction handlers is shuffled each build
As the result - smaller output and each build looks different.
### `vmBytecodeEncoding`
Type: `boolean` Default: `false`
Encodes each bytecode instruction. Instructions are decoded one at a time during execution.
### `vmBytecodeArrayEncoding`
Type: `boolean` Default: `false`
Encodes the entire bytecode array as a single block. The array is decoded once at startup before execution begins. Use together with `vmBytecodeEncoding` for two layers of protection.
### `vmBytecodeArrayEncodingKey`
Type: `string` Default: `''`
Custom encryption key for bytecode array encoding. When set, this key is used instead of the default environment-derived key. The key must be provided at runtime via `vmBytecodeArrayEncodingKeyGetter`.
This option externalizes the encryption key - it's not embedded in the obfuscated code itself. While the key is still accessible at runtime (and thus not truly secret), this separation prevents static analysis tools from finding the key by examining the code alone.
**Important:** The key must be available **synchronously** when the obfuscated code loads. Use synchronous storage like cookies, localStorage, sessionStorage, global variables, or DOM elements (e.g., server-injected meta tags). Async methods like `fetch()` cannot be used directly in the key getter expression.
### `vmBytecodeArrayEncodingKeyGetter`
Type: `string` Default: `''`
**Synchronous** JavaScript expression that **returns** the encryption key at runtime. This expression is evaluated when the obfuscated code loads, and must return the same key that was provided in `vmBytecodeArrayEncodingKey`.
**The obfuscated code will only work when the key getter returns exactly the same key that was used during obfuscation.** If the keys don't match, decryption will fail and the code will produce garbage or errors. If the key getter returns `undefined`, `null`, or an empty string, the code will throw an error: "VM decryption key not available".
**Important:** The key should NOT be defined in the same JavaScript file/script as the obfuscated code. Doing so defeats the purpose of key externalization, as static analysis could still find the key. Store the key in a separate source: server-set cookies, localStorage populated by another script, server-injected HTML meta tags, or a global variable set by a different script that loads before the obfuscated code.
Examples:
```ts
// From cookie
vmBytecodeArrayEncodingKeyGetter: "document.cookie.match(/vmKey=([^;]+)/)?.[1]"
// From localStorage
vmBytecodeArrayEncodingKeyGetter: "localStorage.getItem('vmKey')"
// From global variable
vmBytecodeArrayEncodingKeyGetter: "window.__VM_KEY__"
// From meta tag (server-injected)
vmBytecodeArrayEncodingKeyGetter: "document.querySelector('meta[name=\"vm-key\"]').content"
// From nested object
vmBytecodeArrayEncodingKeyGetter: "window.config.encryption.key"
```
**Usage example:**
```ts
// Build time
JavaScriptObfuscator.obfuscate(code, {
vmObfuscation: true,
vmBytecodeArrayEncoding: true,
vmBytecodeArrayEncodingKey: 'mySecretKey123',
vmBytecodeArrayEncodingKeyGetter: 'window.__VM_KEY__'
});
// Runtime - key must be set before obfuscated code runs
window.__VM_KEY__ = 'mySecretKey123';
```
### `vmAsyncExecutor`
Type: `boolean` Default: `false`
Enables the asynchronous VM executor, which lets [`vmBytecodeArrayEncodingKeyGetter`](#vmbytecodearrayencodingkeygetter) return a `Promise` (an **asynchronous** key getter) — so the decryption key can be fetched at runtime (network request, IndexedDB, etc.) instead of having to be available synchronously when the code loads.
**Heavily recommended for fully async codebases.** In this mode only `async` functions are virtualized — a synchronous function can't be made async without turning its return value into a `Promise` and breaking its callers — so code that is `async` throughout gets the most coverage. It still works when the root is synchronous (e.g. a sync IIFE / UMD wrapper): the outermost `async` functions inside are protected, and the sync parts are left as-is.
**What gets transformed:** every **outermost** `async` function, wherever it appears (including nested inside sync wrappers). The outermost async in each chain is the protected unit — everything inside it, sync and async, is compiled in. Synchronous functions and plain generators are left unobfuscated.
```js
function foo() { // sync — left as-is
function bar() {} // sync — left as-is
async function baz() { // transformed
// any code here, including calls to other async or sync functions
}
async function bark() { // transformed
// any code here, including calls to other async or sync functions
}
}
```
**Skips and warnings.** Async generators are also left unobfuscated when an asynchronous key getter is active (an async generator must return its iterator synchronously and can't wait for the key). In the default `vmTargetFunctionsMode: 'root'` skips are silent (selection is automatic); in `comment` [mode](#vmtargetfunctionsmode) a warning is emitted through `ObfuscationResult.getWarnings()` whenever a function you explicitly marked can't be virtualized — it turned out synchronous, or it's an async generator under an async key getter.
The asynchronous key getter additionally requires `vmBytecodeArrayEncoding` with a `vmBytecodeArrayEncodingKeyGetter`.
**Usage example:**
```ts
JavaScriptObfuscator.obfuscate(code, {
vmObfuscation: true,
vmAsyncExecutor: true,
vmBytecodeArrayEncoding: true,
vmBytecodeArrayEncodingKey: 'mySecretKey123',
// the key getter may now return a Promise
vmBytecodeArrayEncodingKeyGetter: 'fetch("/vm-key").then((res) => res.text())'
});
```
### `vmJumpsEncoding`
Type: `boolean` Default: `false`
Encodes jump targets in the bytecode. Jump offsets are calculated at runtime, hiding the control flow structure (`if`/`else`, loops, etc.) from static analysis.
### `vmDecoyOpcodes`
Type: `boolean` Default: `false`
Adds fake opcode handlers to the VM dispatcher that are never called. For example, if the VM uses 20 real opcodes, this might add 30 fake handlers, making the interpreter appear more complex than it really is.
### `vmDeadCodeInjection`
Type: `boolean` Default: `false`
Injects fake bytecode sequences that are never executed. These look like real instructions but are skipped during runtime, confusing analysis tools that process them.
### `vmMacroOps`
Type: `boolean` Default: `false`
Combines common instruction sequences into single "macro" opcodes. For example, `LOAD + ADD + STORE` might become a single `MACRO_ADD_TO_VAR` instruction. This breaks pattern recognition and can improve performance.
### `vmDebugProtection`
Type: `boolean` Default: `false`
Adds multi-layered anti-debugging, anti-analysis, and anti-LLM defenses to the VM runtime. For best results, allow `unsafe-eval` in your Content Security Policy. Works best with `browser`/`browser-no-eval` targets.
### `vmSelfDefending`
Type: `boolean` Default: `false`
Adds multi-layered tamper detection, anti-hooking, and anti-reverse-engineering protection to the VM runtime.
> :warning: This option force-enables [`vmBytecodeArrayEncoding`](#vmbytecodeArrayEncoding).
Strongly recommended to use together with [`vmDebugProtection`](#vmDebugProtection), [`vmBytecodeArrayEncodingKey`](#vmbytecodeArrayEncodingKey), and [`vmBytecodeArrayEncodingKeyGetter`](#vmbytecodeArrayEncodingKeyGetter).
### `vmDefenseHook`
Type: `{ name: string, aliases?: object }` Default: `''`
`vmDefenseHook` takes an object with two keys: **`name`** (required) and **`aliases`** (optional).
`name` is a **global function your host page defines** that a VM defense (`vmDebugProtection` / `vmSelfDefending`) calls with a signal object when it detects a hostile signal — a debugger or inspector, a headless / automation browser, an AI-coding-agent process, a disallowed domain, and so on. Use it to report the event to your backend (e.g. `navigator.sendBeacon`). The hook is a **pure telemetry sink**: its return value is ignored, and a missing or throwing hook is a silent no-op that can never disable a defense. To change what a defense *does* on detection, use [`vmDefenseReaction`](#vmdefensereaction).
`aliases` optionally renames the fields of that signal object — covered under *Renaming the signal fields* below.
**The signal object.** The hook receives a single `signal`:
- `source` — the specific detector that fired (see the table).
- `category` — the group it reports under: `automation` (non-human browsers), `debugger` (a debugger/inspector is active), `sandbox` (instrumented/fake host), `domain` (domain-lock violation), `tamper` (built-ins patched at runtime), or `integrity` (the VM's own code was altered).
- `score` / `threshold` — how strongly the detector fired and the value it had to reach; the hook fires only once `score >= threshold`. Most checks are all-or-nothing (a single decisive signal); `headless` sums several browser-shape signals, so its `score` is typically higher than its `threshold`.
| `source` | detects | `category` |
|---|----------------------------------------------------------------------------------|---|
| `integrity` | the obfuscated VM code itself has been modified | `integrity` |
| `node` | browser-targeted code running under Node.js | `debugger` |
| `debugger` | an attached or active debugger or inspector session, or a debug environment | `debugger` |
| `headless` | a headless browser is used to run the code | `automation` |
| `agent` | an AI coding-agent running the code | `automation` |
| `timing` | an execution pause suggesting a breakpoint or a stepping debugger | `debugger` |
| `sandbox` | the code runs in a sandbox or a faked host environment | `sandbox` |
| `domain` | the page origin is not in the [`vmDomainLock`](#vmdomainlock) allow-list | `domain` |
| `nativeHook` | a native built-in function has been replaced or hooked | `tamper` |
**Registering the hook.** Define it as a plain global **before** the obfuscated bundle loads — the VM runtime and its defenses run before your (protected) program, so many detections fire during startup:
```js
// in your page, before the obfuscated script:
window.__vmDetection = function (signal) { navigator.sendBeacon('/vm-defense', JSON.stringify(signal)); };
```
```js
// obfuscation option:
vmDefenseHook: { name: '__vmDetection' }
```
> A hook defined *inside* the obfuscated source is registered too late to catch startup-time detections, and if it gets VM-compiled it can't be reached until your program runs. It's kept safe either way (a missing hook no-ops, and a re-entrancy guard prevents any runaway), but for complete coverage register it up front. To still protect your reporting logic, keep the registered hook a one-line buffer (`(window.__vmDet = window.__vmDet || []).push(signal)`) and read/send that buffer from your obfuscated code.
**Renaming the signal fields (`aliases`).** The default `source`/`category` values are descriptive names, so anyone instrumenting the callback (or reading the output) can recognise the protection and which detector fired. `aliases` renames signal fields to opaque tokens of your choice, applied inside the VM *before* the signal is emitted, so those names never appear in the output or reach the callback. Your app knows its own mapping and forwards the tokens to your backend.
Aliases are per field, keeping key and value renames separate: each field takes a `key` (the property name the callback receives); the string name-fields `source` and `category` also take a `values` map, while `score`/`threshold` are numbers and take only a `key`. The names you can map (anything else is rejected at build time):
- **field keys** — `source`, `category`, `score`, `threshold`
- **`source` values** — `headless`, `agent`, `node`, `debugger`, `timing`, `sandbox`, `domain`, `nativeHook`, `integrity`
- **`category` values** — `automation`, `debugger`, `sandbox`, `domain`, `tamper`, `integrity`
```js
vmDefenseHook: {
name: '__vmDetection',
aliases: {
source: { key: 'a8Qm', values: { headless: 'xP4m9Q' } },
category: { key: 'p3Tx', values: { automation: 'bQ7s1M' } },
score: { key: 's1' },
threshold: { key: 't1' }
}
// the callback now receives e.g. { a8Qm: 'xP4m9Q', p3Tx: 'bQ7s1M', s1: <score>, t1: <threshold> }
}
```
This is fingerprint avoidance, not secrecy — the mapping can still be inferred by repeated testing — so its only benefit is not exposing stable, self-explanatory names. Unset entries keep their default names.
> A bare string (`vmDefenseHook: '__vmDetection'`) is accepted as shorthand for `{ name: '__vmDetection' }` but is **deprecated** — prefer the object form.
### `vmDefenseReaction`
Type: `object` Default: `{ automation: 'break', debugger: 'decoy', sandbox: 'decoy', domain: 'break', tamper: 'break', integrity: 'break' }`
Configures how each detection category reacts. It does **not** enable anything — the defenses themselves are turned on by [`vmSelfDefending`](#vmselfdefending), [`vmDebugProtection`](#vmdebugprotection), and [`vmDomainLock`](#vmdomainlock); this option only selects *how* an enabled defense reacts. The **category is the unit of control** — every detector in a category enacts that category's reaction.
Each **category** groups the detectors that watch for one kind of hostile condition. A category only reacts when the option that emits its detectors is enabled:
| Category | Enabled by | Reacts when |
|---|---|---|
| `automation` | `vmSelfDefending` or `vmDebugProtection` | The code is being driven by software instead of a person: a headless or automated browser, a scraping / testing framework, or an AI coding-agent stepping the page. |
| `debugger` | `vmDebugProtection` or `vmSelfDefending` | Someone has a debugger or the browser's developer-tools inspector open and is stepping through the running code to understand it. |
| `sandbox` | `vmDebugProtection` | The code is not running in a real browser at all — it has been lifted into an emulated or scripted JavaScript environment to be executed and studied offline. |
| `domain` | `vmDomainLock` | The code is running on a site you did not authorize: a host not in your [`vmDomainLock`](#vmdomainlock) allow-list (for example, your bundle copied onto someone else's domain). |
| `tamper` | `vmSelfDefending` | The JavaScript environment around the VM has been modified to watch or hijack it, such as native browser built-ins swapped out for instrumented versions. |
| `integrity` | `vmSelfDefending` | The protected bundle's own code has been edited or patched since you generated it. |
Every category maps to one or more of [`vmSelfDefending`](#vmselfdefending), [`vmDebugProtection`](#vmdebugprotection), and [`vmDomainLock`](#vmdomainlock); there is no category outside those three options, and a reaction set for a category whose option is off simply has no effect.
Keys are these six category names, or `default` (a fallback for unspecified categories). Values are:
- `break` — break immediately
- `decoy` — keep running on poisoned state, silently producing wrong results
- `none` — do nothing locally (telemetry only)
The per-category defaults are shown above; a category you don't set (or set to its default value) uses that default. `default` reaches **every** category, including the correct-by-construction ones (`integrity`, `tamper`), so `{ default: 'none' }` is a genuinely non-breaking, telemetry-only build:
```js
vmDefenseReaction: { default: 'none' } // never break — pair with vmDefenseHook
vmDefenseReaction: { automation: 'none', domain: 'break' } // tolerate automation FPs, still break on a bad domain
```
### `browserEnvironment`
Type: `object` Default: `{}`
Declares facts about the environment your production build is served in, so the protected code can bind itself to them. Only takes effect together with [`vmSelfDefending`](#vmselfdefending), and only for `browser` / `browser-no-eval` / `service-worker` targets — it is rejected for `node`, `userscript`, and `bytenode`.
Currently one field:
- **`transport`** — the scheme your production serves the bundle over: `'http'` or `'https'`. With `'https'`, the build ties its integrity to being served over HTTPS, so a copy an analyst lifts and serves over plain HTTP (a common local reverse-engineering setup) will not run correctly. `'http'` or an unset field adds no binding.
```js
browserEnvironment: { transport: 'https' }
```
> :warning: A build declared `transport: 'https'` runs correctly **only** where it is actually served over `https:`. Every other scheme corrupts it, so declare it only when every context that loads your production build is HTTPS. That excludes: plain `http://` (including `http://localhost` in development), `file://` (Electron / Cordova / packaged apps), and `blob:` / `about:` embeddings (a bundle running inside an `about:blank` or `srcdoc` iframe). A client-side HTTP→HTTPS redirect still renders the HTTP page first, so the bundle must not run before the redirect completes.
### `vmStatefulOpcodes`
Type: `boolean` Default: `false`
Makes opcode meanings depend on position in the bytecode. Each position has a different opcode-to-handler mapping derived from a seed, so the same opcode number performs different operations at different positions.
### `vmCallContextOpcodes`
Type: `boolean` Default: `false`
Makes a protected function depend on where it's called from, so it can't be lifted out of the code and run or analyzed on its own — it only behaves correctly when invoked through its real call sites in the program. This option affects runtime performance.
Currently only the following constructions are supported:
- function declarations (`function f() {}`);
- function expressions and arrow functions assigned to a variable (`const f = () => {}`);
- instance private methods (`this.#m()`).
In every case the function must always be reached through a direct call (`f()`, `this.#m()`). If it is stored in another variable, passed as an argument, or otherwise used as a value, it is left unprotected. Async functions are supported; generators are not.
This option is experimental and may break your code, so test the output thoroughly before using it.
### `vmStackEncoding`
Type: `boolean` Default: `false`
Encrypts values on the VM stack during execution. Values are encoded when pushed and decoded when popped, so memory inspection shows encrypted data instead of actual values.
This option heavily affects performance.
### `vmCompactDispatcher`
Type: `boolean` Default: `false`
Uses a single VM executor instead of dual executors (sync + generator). Reduces obfuscated code size but adds ~20% performance overhead on recursion-heavy code.
- `false` (default): dual executors — optimal performance, larger output
- `true`: single executor — smaller output, slightly slower
### `vmRegisterBased`
Type: `boolean` Default: `false`
Switches the VM from the default stack-based bytecode to a register-based execution model, which improves VM runtime performance in some cases by ~15-20%, but slightly increases obfuscated code size.
Because it emits a structurally different bytecode and executor, it also gives the VM a more unique fingerprint than the default stack-based one — use it when you want to vary the VM's shape so it is less recognizable to generic analysis.
Under the hood this isn't a native register-based compiler — the regular stack-based compiler still generates the bytecode, which a separate transformation stage then rewrites into register-based form.
This option is experimental - test that your code runs well when `vmRegisterBased` is enabled.
### `vmStringArrayBytecodeOnly`
Type: `boolean` Default: `false`
When enabled, the string array will **only** extract strings from bytecode data — no other strings in the code are transformed. This force-enables `stringArray` even if it's not explicitly set.
**Why use this:** Extracting all VM runtime strings to a string array is slow. This option targets only bytecode content for string array extraction, improving performance while still protecting bytecode constants.
- When `vmBytecodeArrayEncoding: false` — strings inside bytecode constant pools (`c` arrays) are extracted
- When `vmBytecodeArrayEncoding: true` — top-level base64 encoded bytecode strings are extracted
- `stringArrayThreshold` still controls what percentage of those bytecode strings are extracted
### `vmDomainLock`
Type: `string[]` Default: `[]`
##### :warning: This option does not work with `target: 'node'`, `target: 'service-worker'` or `target: 'bytenode'`
Restricts the obfuscated code to specific domains and/or sub-domains, and is much harder to locate and strip than `domainLock`.
If the source code isn't run on the domains specified by this option, the browser will be redirected to the URL passed to [`vmDomainLockRedirectUrl`](#vmdomainlockredirecturl), and further protected calls will return incorrect results even if the redirect is suppressed.
##### Multiple domains and sub-domains
It's possible to lock your code to more than one domain or sub-domain. For instance, to lock it so the code only runs on **www.example.com** add `www.example.com`. To make it work on the root domain including any sub-domains (`example.com`, `sub.example.com`), use `.example.com`.
### `vmDomainLockRedirectUrl`
Type: `string` Default: `about:blank`
##### :warning: This option does not work with `target: 'node'`, `target: 'service-worker'` or `target: 'bytenode'`
Allows the browser to be redirected to a passed URL if the source code isn't run on the domains specified by [`vmDomainLock`](#vmdomainlock).
### `strictMode`
Type: `boolean | null` Default: `null`
Allows to specify how the obfuscator should treat code regarding JavaScript strict mode.
Available values:
* `null` (default) - auto-detect strict mode from the code. If the code has explicit `'use strict'` directive, ES module syntax, or class methods, it's treated as strict mode. Otherwise, sloppy mode is assumed.
* `true` - force strict mode treatment for all code, even without explicit `'use strict'` directive. Use this when your code will run in strict mode context (e.g., in ES modules, bundlers, or modern frameworks).
* `false` - only explicit strict mode indicators (`'use strict'`, ES modules, class methods) are treated as strict. Parent scope inheritance still applies per JS spec.
### `parseHtml`
Type: `boolean` Default: `false`
Enables obfuscation of JavaScript within HTML `<script>` tags.
When enabled, the obfuscator will:
- Auto-detect if input is HTML (by checking for `<!DOCTYPE`, `<html>`, `<head>`, `<body>`, or `<script>` tags)
- Extract JavaScript from `<script>` tags marked with the `data-javascript-obfuscator` attribute
- Obfuscate each marked script individually while preserving the HTML structure
- Inject obfuscated code back into the original positions
**Important:** Only scripts with the `data-javascript-obfuscator` attribute are obfuscated. Each marked script is obfuscated individually and independently. This means:
- Code inside marked script tags **must be isolated** - it must NOT reference variables, functions, or classes defined in other marked script tags
- Unmarked scripts can still access globals defined by marked scripts (via `var` declarations or explicit `globalThis` assignments)
- This gives you explicit control over which scripts to protect
**Obfuscated (must have `data-javascript-obfuscator` attribute):**
- `<script data-javascript-obfuscator>` - regular scripts
- `<script type="text/javascript" data-javascript-obfuscator>` - explicitly typed scripts
- Scripts with any additional attributes (`id`, `class`, other `data-*`, etc.)
**Skipped (left unchanged):**
- Scripts without `data-javascript-obfuscator` attribute
- `<script type="module">` - ES modules (even with the attribute)
- `<script src="...">` - external scripts (even with the attribute)
- Empty script tags
**Note:** Source maps are not generated when `parseHtml` is enabled, as they would not map correctly to the HTML output.
Example:
```ts
// input
const html = `<!DOCTYPE html>
<html>
<body>
<!-- This script will NOT be obfuscated -->
<script>
var helper = 'utility';
</script>
<!-- This script WILL be obfuscated -->
<script data-javascript-obfuscator>
var greeting = 'Hello World';
console.log(greeting);
</script>
</body>
</html>`;
JavaScriptObfuscator.obfuscate(html, {
parseHtml: true,
stringArray: true
});
// output: HTML with only the marked script obfuscated
```
### `randomIdentifiersPrefix`
Type: `boolean` Default: `false`
Appends a seeded random prefix (6 alphanumeric characters) to all global identifiers. Use this option to avoid collisions between separately obfuscated bundles that are loaded into the same global scope — it removes the need to pick a unique `identifiersPrefix` per bundle manually.
- The random value is derived from the `seed` option and the source code hash, so reproducible builds with the same seed produce the same prefix.
- When combined with `identifiersPrefix`, the random characters are appended to the user-provided prefix (e.g. `myApp` + random `aBc123` → `myAppaBc123`).
- When combined with `vmObfuscation`, the random value replaces the default `vm` prefix — randomness already guarantees uniqueness.
## Frequently Asked Questions
### What javascript versions are supported?
`es3`, `es5`, `es2015`, `es2016`, `es2017`, `es2018`, `es2019` and partially `es2020`
### I want to use feature that described in `README.md` but it's not working!
The README on the master branch might not match that of the latest stable release.
### Why CLI command not working?
Try to run `npm link javascript-obfuscator` command or install it globally with `npm i -g javascript-obfuscator`
### Online version?
[obfuscator.io](https://obfuscator.io)
### JSX support?
No. JSX support isn't planned.
### How to change kind of variables of inserted nodes (`var`, `let` or `const`)?
See: [`Kind of variables`](#kind-of-variables)
### Why I got `null` value instead of `BigInt` number?
`BigInt` obfuscation works correctly only in environments that support `BigInt` values. See [ESTree spec](https://github.com/estree/estree/blob/master/es2020.md#bigintliteral)
### I enabled `renameProperties` option, and my code broke! What to do?
Try `renamePropertiesMode: 'safe'` option, if it still doesn't work, just disable this option.
## GitHub Sponsors
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## Backers
Support us with a monthly donation and help us continue our activities. [[Become a backer](https://opencollective.com/javascript-obfuscator#backer)]
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## Open Collective Sponsors
Become a sponsor and get your logo on our README on Github with a link to your site.
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## License
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Copyright (C) 2016-2026 [Timofei Kachalov](http://github.com/sanex3339).
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.