workflow/docs/api-reference/workflow-globals.mdx

Workflow SDK - Build durable, resilient, and observable workflows

---
title: Workflow Globals
description: Global APIs available inside workflow functions.
type: reference
summary: Reference of all global APIs available inside workflow functions.
prerequisites:
  - /docs/foundations/workflows-and-steps
related:
  - /docs/errors/node-js-module-in-workflow
  - /docs/errors/fetch-in-workflow
  - /docs/errors/timeout-in-workflow
  - /docs/how-it-works/code-transform
---

Workflow functions run in a restricted environment that prevents access to non-deterministic or side-effecting APIs. This page lists all global APIs available inside `"use workflow"` functions.

For full Node.js runtime access, use [step functions](/docs/foundations/workflows-and-steps#step-functions).

## Deterministic APIs

These APIs are available but are **seeded or fixed** to ensure deterministic behavior across replays.

| API | Behavior |
|-----|----------|
| [`Math.random()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/random) | Seeded random number generator — same seed produces the same sequence every replay |
| [`Date`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date) / `Date.now()` / `new Date()` | Returns a fixed timestamp that advances with the workflow's logical clock |
| [`crypto.getRandomValues()`](https://developer.mozilla.org/en-US/docs/Web/API/Crypto/getRandomValues) | Seeded — produces deterministic output for a given workflow run |
| [`crypto.randomUUID()`](https://developer.mozilla.org/en-US/docs/Web/API/Crypto/randomUUID) | Seeded — produces deterministic UUIDs for a given workflow run |
| [`crypto.subtle.digest()`](https://developer.mozilla.org/en-US/docs/Web/API/SubtleCrypto/digest) | Passes through to the real implementation (SHA-256, etc. are deterministic by nature) |

<Callout type="info">
You can safely use `Math.random()`, `Date.now()`, and `crypto.randomUUID()` in workflow functions. The framework ensures these return the same values across replays.
</Callout>

## Web Platform APIs

These standard Web APIs are available in workflow functions:

- [`Headers`](https://developer.mozilla.org/en-US/docs/Web/API/Headers)
- [`TextEncoder`](https://developer.mozilla.org/en-US/docs/Web/API/TextEncoder) / [`TextDecoder`](https://developer.mozilla.org/en-US/docs/Web/API/TextDecoder)
- [`URL`](https://developer.mozilla.org/en-US/docs/Web/API/URL) / [`URLSearchParams`](https://developer.mozilla.org/en-US/docs/Web/API/URLSearchParams)
- [`Request`](https://developer.mozilla.org/en-US/docs/Web/API/Request) / [`Response`](https://developer.mozilla.org/en-US/docs/Web/API/Response) — custom implementations with [special behavior in the workflow context](/docs/foundations/serialization#request--response). Body methods like `.json()` and `.text()` are automatically treated as step invocations.
- [`console`](https://developer.mozilla.org/en-US/docs/Web/API/console)
- [`structuredClone`](https://developer.mozilla.org/en-US/docs/Web/API/Window/structuredClone)
- [`atob`](https://developer.mozilla.org/en-US/docs/Web/API/Window/atob) / [`btoa`](https://developer.mozilla.org/en-US/docs/Web/API/Window/btoa)

## Environment Variables

`process.env` is available as a **read-only, frozen** snapshot of the environment variables at the time the workflow was started. You cannot modify it.

```typescript
export async function myWorkflow() {
  "use workflow";

  const apiKey = process.env.API_KEY; // works
  process.env.FOO = "bar"; // throws — process.env is frozen
}
```

## Binary Data

Standard JavaScript typed arrays (`Uint8Array`, `Int32Array`, `Float64Array`, etc.) are available in workflow functions.

### Base64 and hex encoding

The workflow environment provides [`Uint8Array` base64 and hex methods](https://tc39.es/proposal-arraybuffer-base64/) for encoding and decoding binary data:

{/* @skip-typecheck: polyfilled methods not available in host TypeScript */}
```typescript
// Encode to base64
const bytes = new Uint8Array([72, 101, 108, 108, 111]);
bytes.toBase64(); // "SGVsbG8="
bytes.toBase64({ alphabet: "base64url" }); // URL-safe variant
bytes.toBase64({ omitPadding: true }); // "SGVsbG8"

// Decode from base64
Uint8Array.fromBase64("SGVsbG8="); // Uint8Array([72, 101, 108, 108, 111])

// Encode to hex
bytes.toHex(); // "48656c6c6f"

// Decode from hex
Uint8Array.fromHex("48656c6c6f"); // Uint8Array([72, 101, 108, 108, 111])

// Write into an existing array
const target = new Uint8Array(5);
target.setFromBase64("SGVsbG8="); // { read: 8, written: 5 }
target.setFromHex("48656c6c6f"); // { read: 10, written: 5 }
```

<Callout type="info">
These methods are polyfilled in the workflow environment. When the JavaScript runtime ships native support, the polyfill is automatically bypassed.
</Callout>

## Not Available

The following are **not available** in workflow functions. Move this logic to [step functions](/docs/foundations/workflows-and-steps#step-functions) instead.

- **Node.js core modules**: `fs`, `path`, `http`, `https`, `net`, `dns`, `child_process`, `cluster`, `os`, `stream`, `crypto` (Node.js version), etc. See [node-js-module-in-workflow](/docs/errors/node-js-module-in-workflow).
- **Global `fetch`**: Use [`import { fetch } from "workflow"`](/docs/api-reference/workflow/fetch) instead. See [fetch-in-workflow](/docs/errors/fetch-in-workflow).
- **Timers**: `setTimeout`, `setInterval`, `setImmediate`, and their `clear*` counterparts. Use [`sleep()`](/docs/api-reference/workflow/sleep) instead. See [timeout-in-workflow](/docs/errors/timeout-in-workflow).
- **`Buffer`**: Node.js-specific API. Use `Uint8Array` with `toBase64()` / `fromBase64()` / `toHex()` / `fromHex()` for binary data encoding, or `atob()` / `btoa()` for string-based base64.