bun-types

--- title: HTML & static sites description: Build static sites, landing pages, and web applications with Bun's bundler --- Bun's bundler has first-class support for HTML. Build static sites, landing pages, and web applications with zero configuration. Just point Bun at your HTML file and it handles everything else. ```html title="index.html" icon="file-code" <!doctype html> <html> <head> <link rel="stylesheet" href="./styles.css" /> <script src="./app.ts" type="module"></script> </head> <body> <img src="./logo.png" /> </body> </html> ``` To get started, pass HTML files to `bun`. ```bash terminal icon="terminal" bun ./index.html ``` ``` Bun v1.3.3 ready in 6.62ms → http://localhost:3000/ Press h + Enter to show shortcuts ``` Bun's development server provides powerful features with zero configuration: - **Automatic Bundling** - Bundles and serves your HTML, JavaScript, and CSS - **Multi-Entry Support** - Handles multiple HTML entry points and glob entry points - **Modern JavaScript** - TypeScript & JSX support out of the box - **Smart Configuration** - Reads `tsconfig.json` for paths, JSX options, experimental decorators, and more - **Plugins** - Plugins for TailwindCSS and more - **ESM & CommonJS** - Use ESM and CommonJS in your JavaScript, TypeScript, and JSX files - **CSS Bundling & Minification** - Bundles CSS from `<link>` tags and `@import` statements - **Asset Management** - Automatic copying & hashing of images and assets; Rewrites asset paths in JavaScript, CSS, and HTML ## Single Page Apps (SPA) When you pass a single `.html` file to Bun, Bun will use it as a fallback route for all paths. This makes it perfect for single page apps that use client-side routing: ```bash terminal icon="terminal" bun index.html ``` ``` Bun v1.3.3 ready in 6.62ms → http://localhost:3000/ Press h + Enter to show shortcuts ``` Your React or other SPA will work out of the box — no configuration needed. All routes like `/about`, `/users/123`, etc. will serve the same HTML file, letting your client-side router handle the navigation. ```html title="index.html" icon="file-code" <!doctype html> <html> <head> <title>My SPA</title> <script src="./app.tsx" type="module"></script> </head> <body> <div id="root"></div> </body> </html> ``` ## Multi-page apps (MPA) Some projects have several separate routes or HTML files as entry points. To support multiple entry points, pass them all to `bun`: ```bash terminal icon="terminal" bun ./index.html ./about.html ``` ```txt Bun v1.3.3 ready in 6.62ms → http://localhost:3000/ Routes: / ./index.html /about ./about.html Press h + Enter to show shortcuts ``` This will serve: - `index.html` at `/` - `about.html` at `/about` ### Glob patterns To specify multiple files, you can use glob patterns that end in `.html`: ```bash terminal icon="terminal" bun ./**/*.html ``` ``` Bun v1.3.3 ready in 6.62ms → http://localhost:3000/ Routes: / ./index.html /about ./about.html Press h + Enter to show shortcuts ``` ### Path normalization The base path is chosen from the longest common prefix among all the files. ```bash terminal icon="terminal" bun ./index.html ./about/index.html ./about/foo/index.html ``` ``` Bun v1.3.3 ready in 6.62ms → http://localhost:3000/ Routes: / ./index.html /about ./about/index.html /about/foo ./about/foo/index.html Press h + Enter to show shortcuts ``` ## JavaScript, TypeScript, and JSX Bun's transpiler natively implements JavaScript, TypeScript, and JSX support. Learn more about loaders in Bun. <Note>Bun's transpiler is also used at runtime.</Note> ### ES Modules & CommonJS You can use ESM and CJS in your JavaScript, TypeScript, and JSX files. Bun will handle the transpilation and bundling automatically. There is no pre-build or separate optimization step. It's all done at the same time. Learn more about module resolution in Bun. ## CSS Bun's CSS parser is also natively implemented (clocking in around 58,000 lines of Zig). It's also a CSS bundler. You can use `@import` in your CSS files to import other CSS files. For example: <CodeGroup> ```css styles.css icon="file-code" @import "./abc.css"; .container { background-color: blue; } ``` ```css abc.css icon="file-code" body { background-color: red; } ``` </CodeGroup> This outputs: ```css styles.css icon="file-code" body { background-color: red; } .container { background-color: blue; } ``` ### Referencing local assets in CSS You can reference local assets in your CSS files. ```css styles.css icon="file-code" body { background-image: url("./logo.png"); } ``` This will copy `./logo.png` to the output directory and rewrite the path in the CSS file to include a content hash. ```css styles.css icon="file-code" body { background-image: url("./logo-[ABC123].png"); } ``` ### Importing CSS in JavaScript To associate a CSS file with a JavaScript file, you can import it in your JavaScript file. ```ts app.ts icon="/icons/typescript.svg" import "./styles.css"; import "./more-styles.css"; ``` This generates `./app.css` and `./app.js` in the output directory. All CSS files imported from JavaScript will be bundled into a single CSS file per entry point. If you import the same CSS file from multiple JavaScript files, it will only be included once in the output CSS file. ## Plugins The dev server supports plugins. ### Tailwind CSS To use TailwindCSS, install the `bun-plugin-tailwind` plugin: ```bash terminal icon="terminal" # Or any npm client bun install --dev bun-plugin-tailwind ``` Then, add the plugin to your `bunfig.toml`: ```toml title="bunfig.toml" icon="settings" [serve.static] plugins = ["bun-plugin-tailwind"] ``` Then, reference TailwindCSS in your HTML via `<link>` tag, `@import` in CSS, or import in JavaScript. <Tabs> <Tab title="index.html"> ```html title="index.html" icon="file-code"  <link rel="stylesheet" href="tailwindcss" /> ``` </Tab> <Tab title="styles.css"> ```css title="styles.css" icon="file-code" @import "tailwindcss"; ``` </Tab> <Tab title="app.ts"> ```ts title="app.ts" icon="/icons/typescript.svg" import "tailwindcss"; ``` </Tab> </Tabs> <Info>Only one of those are necessary, not all three.</Info> ## Inline environment variables Bun can replace `process.env.*` references in your JavaScript and TypeScript with their actual values at build time. This is useful for injecting configuration like API URLs or feature flags into your frontend code. ### Dev server (runtime) To inline environment variables when using `bun ./index.html`, configure the `env` option in your `bunfig.toml`: ```toml title="bunfig.toml" icon="settings" [serve.static] env = "PUBLIC_*" # only inline env vars starting with PUBLIC_ (recommended) # env = "inline" # inline all environment variables # env = "disable" # disable env var replacement (default) ``` <Note> This only works with literal `process.env.FOO` references, not `import.meta.env` or indirect access like `const env = process.env; env.FOO`. If an environment variable is not set, you may see runtime errors like `ReferenceError: process is not defined` in the browser. </Note> Then run the dev server: ```bash terminal icon="terminal" PUBLIC_API_URL=https://api.example.com bun ./index.html ``` ### Build for production When building static HTML for production, use the `env` option to inline environment variables: <Tabs> <Tab title="CLI"> ```bash terminal icon="terminal" # Inline all environment variables bun build ./index.html --outdir=dist --env=inline # Only inline env vars with a specific prefix (recommended) bun build ./index.html --outdir=dist --env=PUBLIC_* ``` </Tab> <Tab title="API"> ```ts title="build.ts" icon="/icons/typescript.svg" // Inline all environment variables await Bun.build({ entrypoints: ["./index.html"], outdir: "./dist", env: "inline", // [!code highlight] }); // Only inline env vars with a specific prefix (recommended) await Bun.build({ entrypoints: ["./index.html"], outdir: "./dist", env: "PUBLIC_*", // [!code highlight] }); ``` </Tab> </Tabs> ### Example Given this source file: ```ts title="app.ts" icon="/icons/typescript.svg" const apiUrl = process.env.PUBLIC_API_URL; console.log(`API URL: ${apiUrl}`); ``` And running with `PUBLIC_API_URL=https://api.example.com`: ```bash terminal icon="terminal" PUBLIC_API_URL=https://api.example.com bun build ./index.html --outdir=dist --env=PUBLIC_* ``` The bundled output will contain: ```js title="dist/app.js" icon="/icons/javascript.svg" const apiUrl = "https://api.example.com"; console.log(`API URL: ${apiUrl}`); ``` ## Echo console logs from browser to terminal Bun's dev server supports streaming console logs from the browser to the terminal. To enable, pass the `--console` CLI flag. ```bash terminal icon="terminal" bun ./index.html --console ``` ``` Bun v1.3.3 ready in 6.62ms → http://localhost:3000/ Press h + Enter to show shortcuts ``` Each call to `console.log` or `console.error` will be broadcast to the terminal that started the server. This is useful to see errors from the browser in the same place you run your server. This is also useful for AI agents that watch terminal output. Internally, this reuses the existing WebSocket connection from hot module reloading to send the logs. ## Edit files in the browser Bun's frontend dev server has support for Automatic Workspace Folders in Chrome DevTools, which lets you save edits to files in the browser. ## Keyboard Shortcuts While the server is running: - `o + Enter` - Open in browser - `c + Enter` - Clear console - `q + Enter` (or `Ctrl+C`) - Quit server ## Build for Production When you're ready to deploy, use `bun build` to create optimized production bundles: <Tabs> <Tab title="CLI"> ```bash terminal icon="terminal" bun build ./index.html --minify --outdir=dist ``` </Tab> <Tab title="API"> ```ts title="build.ts" icon="/icons/typescript.svg" await Bun.build({ entrypoints: ["./index.html"], outdir: "./dist", minify: true, }); ``` </Tab> </Tabs> <Warning> Currently, plugins are only supported through `Bun.build`'s API or through `bunfig.toml` with the frontend dev server - not yet supported in `bun build`'s CLI. </Warning> ### Watch Mode You can run `bun build --watch` to watch for changes and rebuild automatically. This works nicely for library development. <Info>You've never seen a watch mode this fast.</Info> ## Plugin API Need more control? Configure the bundler through the JavaScript API and use Bun's builtin `HTMLRewriter` to preprocess HTML. ```ts title="build.ts" icon="/icons/typescript.svg" await Bun.build({ entrypoints: ["./index.html"], outdir: "./dist", minify: true, plugins: [ { // A plugin that makes every HTML tag lowercase name: "lowercase-html-plugin", setup({ onLoad }) { const rewriter = new HTMLRewriter().on("*", { element(element) { element.tagName = element.tagName.toLowerCase(); }, text(element) { element.replace(element.text.toLowerCase()); }, }); onLoad({ filter: /\.html$/ }, async args => { const html = await Bun.file(args.path).text(); return { // Bun's bundler will scan the HTML for <script> tags, <link rel="stylesheet"> tags, and other assets // and bundle them automatically contents: rewriter.transform(html), loader: "html", }; }); }, }, ], }); ``` ## What Gets Processed? Bun automatically handles all common web assets: - **Scripts** (`<script src>`) are run through Bun's JavaScript/TypeScript/JSX bundler - **Stylesheets** (`<link rel="stylesheet">`) are run through Bun's CSS parser & bundler - **Images** (`<img>`, `<picture>`) are copied and hashed - **Media** (`<video>`, `<audio>`, `<source>`) are copied and hashed - Any `<link>` tag with an `href` attribute pointing to a local file is rewritten to the new path, and hashed All paths are resolved relative to your HTML file, making it easy to organize your project however you want. <Warning> **This is a work in progress** - Need more plugins - Need more configuration options for things like asset handling - Need a way to configure CORS, headers, etc. {/* todo: find the correct link to link to as this 404's and there isn't any similar files */} {/* If you want to submit a PR, most of the code is [here](https://github.com/oven-sh/bun/blob/main/src/bun.js/api/bun/html-rewriter.ts). You could even copy paste that file into your project and use it as a starting point. */} </Warning> ## How this works This is a small wrapper around Bun's support for HTML imports in JavaScript. ## Adding a backend to your frontend To add a backend to your frontend, you can use the "routes" option in `Bun.serve`. Learn more in the full-stack docs.