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The workerd runtime provides a rich set of global APIs that are automatically available in your workers without requiring imports.

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Global objects

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console
Console
Console logging methods for debugging and output.Methods: log(), debug(), info(), warn(), error(), trace(), dir(), dirxml(), table(), time(), timeEnd(), timeLog(), group(), groupEnd(), groupCollapsed(), assert(), count(), countReset(), clear()
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crypto
Crypto
Cryptographic operations via the Web Crypto API.Properties:
  • subtle: SubtleCrypto interface for advanced cryptographic operations
  • getRandomValues(): Generate cryptographically strong random values
  • randomUUID(): Generate a random UUID
See Crypto API for details.
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caches
CacheStorage
Cache API for storing HTTP responses.
  • default: Default cache
  • open(name): Open a named cache
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scheduler
Scheduler
Task scheduling interface.
  • wait(delay): Create a promise that resolves after a delay
  • wait(delay, options): Wait with abort signal support
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performance
Performance
Performance timing and measurement.
  • now(): High-resolution timestamp
  • timeOrigin: Time origin as DOMHighResTimeStamp
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navigator
Navigator
Navigator object with user agent information.
  • userAgent: User agent string

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Global functions

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fetch()
function
Make HTTP requests.
function fetch(
  input: RequestInfo,
  init?: RequestInit
): Promise<Response>
See Fetch API for details.
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addEventListener()
function
Register event listeners for worker events.
function addEventListener(
  type: string,
  listener: EventListener
): void
Supported events: fetch, scheduled, queue, alarm, trace, tail
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removeEventListener()
function
Remove previously registered event listeners.
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dispatchEvent()
function
Dispatch a custom event.
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atob()
function
Decode a base64-encoded string.
function atob(data: string): string
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btoa()
function
Encode a string to base64.
function btoa(data: string): string
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setTimeout()
function
Schedule a function to run after a delay.
function setTimeout(
  handler: TimerHandler,
  timeout?: number,
  ...arguments: any[]
): number
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clearTimeout()
function
Cancel a timer created with setTimeout.
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setInterval()
function
Schedule a function to run repeatedly at intervals.
function setInterval(
  handler: TimerHandler,
  timeout?: number,
  ...arguments: any[]
): number
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clearInterval()
function
Cancel a timer created with setInterval.
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queueMicrotask()
function
Queue a microtask to be executed.
function queueMicrotask(callback: VoidFunction): void
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structuredClone()
function
Create a deep copy of a value using the structured clone algorithm.
function structuredClone<T>(
  value: T,
  options?: StructuredSerializeOptions
): T

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Global constructors

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Request
constructor
Represents an HTTP request.See Fetch API for details.
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Response
constructor
Represents an HTTP response.See Fetch API for details.
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Headers
constructor
Represents HTTP headers.
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URL
constructor
Parse and manipulate URLs.
new URL(url: string, base?: string | URL)
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URLSearchParams
constructor
Parse and manipulate URL query strings.
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ReadableStream
constructor
Represents a readable stream of data.See Streams API for details.
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WritableStream
constructor
Represents a writable stream of data.See Streams API for details.
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TransformStream
constructor
Represents a transform stream that can modify data.See Streams API for details.
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WebSocket
constructor
WebSocket client for bidirectional communication.See WebSocket API for details.
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WebSocketPair
constructor
Create a pair of connected WebSocket objects.
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Event
constructor
Base class for events.
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EventTarget
constructor
Base class for objects that can receive events.
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AbortController
constructor
Create an abort signal for cancellable operations.
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AbortSignal
constructor
Signal for cancelling asynchronous operations.
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TextEncoder
constructor
Encode strings to UTF-8 byte arrays.
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TextDecoder
constructor
Decode byte arrays to strings.
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Blob
constructor
Represents immutable binary data.
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File
constructor
Represents a file with name and metadata.
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FormData
constructor
Represents HTML form data.

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Example usage

// Using global fetch
const response = await fetch('https://api.example.com/data');
const data = await response.json();

// Using crypto
const uuid = crypto.randomUUID();
const randomBytes = new Uint8Array(16);
crypto.getRandomValues(randomBytes);

// Using console
console.log('Worker started');
console.error('Something went wrong', error);

// Using timers
setTimeout(() => {
  console.log('Delayed execution');
}, 1000);

// Using streams
const { readable, writable } = new TransformStream();

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Module syntax

For ES modules syntax, export handlers from your main module: 
export default {
  async fetch(request, env, ctx) {
    return new Response('Hello World!');
  },
  
  async scheduled(event, env, ctx) {
    // Handle scheduled events
  }
}

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Service worker syntax

For service worker syntax, use addEventListener: 
addEventListener('fetch', event => {
  event.respondWith(
    new Response('Hello World!')
  );
});

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