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Documentation Index

Fetch the complete documentation index at: https://mintlify.com/cloudflare/workers-sdk/llms.txt

Use this file to discover all available pages before exploring further.

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Create Your First Worker

Get started with Cloudflare Workers by creating a simple “Hello World” application. This guide will walk you through creating, developing, and deploying your first Worker.
1

Create a new project

Use Create Cloudflare (C3) to scaffold a new Worker project with a single command:
npm create cloudflare@latest
C3 will prompt you with several questions:
╭ Create an application with Cloudflare
│
├ In which directory do you want to create your application?
│ dir ./my-worker
│
├ What type of application do you want to create?
│ type "Hello World" Worker
│
├ Do you want to use TypeScript?
│ yes typescript
│
├ Do you want to deploy your application?
│ no deploy via `npm run deploy`
│
╰ Application created successfully!
Choose TypeScript for better development experience with autocomplete and type checking.
2

Navigate to your project

Change into your newly created project directory:
cd my-worker
Your project structure should look like this:
my-worker/
├── src/
│   └── index.ts        # Your Worker code
├── wrangler.jsonc      # Configuration file
├── package.json        # Dependencies and scripts
├── tsconfig.json       # TypeScript configuration
└── vitest.config.js    # Testing configuration
3

Explore the Worker code

Open src/index.ts to see your Worker code:
src/index.ts
export interface Env {
  // Example binding to KV. Learn more at https://developers.cloudflare.com/workers/runtime-apis/kv/
  // MY_KV_NAMESPACE: KVNamespace;
  //
  // Example binding to Durable Object. Learn more at https://developers.cloudflare.com/workers/runtime-apis/durable-objects/
  // MY_DURABLE_OBJECT: DurableObjectNamespace;
  //
  // Example binding to R2. Learn more at https://developers.cloudflare.com/workers/runtime-apis/r2/
  // MY_BUCKET: R2Bucket;
}

export default {
  async fetch(
    request: Request,
    env: Env,
    ctx: ExecutionContext
  ): Promise<Response> {
    return new Response("Hello World!");
  },
};
This is the default Worker template with:
  • Env interface: Type definitions for bindings (KV, R2, Durable Objects, etc.)
  • fetch handler: The main entry point that handles incoming HTTP requests
  • Request/Response: Standard Web API objects
4

Start the development server

Start Wrangler’s local development server:
npm run dev
You should see output like:
⛅️ wrangler 4.69.0
-------------------

⎔ Starting local server...
[wrangler:inf] Ready on http://localhost:8787
Open your browser to http://localhost:8787 to see your Worker in action!
The development server includes:
  • Hot reloading: Changes are reflected immediately
  • Source maps: Debug TypeScript directly
  • DevTools: Press D in the terminal to open Chrome DevTools
5

Make your first change

Update your Worker to respond with JSON:
src/index.ts
export default {
  async fetch(
    request: Request,
    env: Env,
    ctx: ExecutionContext
  ): Promise<Response> {
    return Response.json({
      message: "Hello from Cloudflare Workers!",
      timestamp: new Date().toISOString(),
      url: request.url,
    });
  },
};
Save the file and refresh your browser. You should see the JSON response immediately!
Try adding more fields to the response or reading request headers with request.headers.get("User-Agent").
6

Deploy to production

When you’re ready to deploy your Worker to Cloudflare’s global network:
npm run deploy
Wrangler will authenticate with Cloudflare (if needed) and deploy your Worker:
⛅️ wrangler 4.69.0
-------------------

Total Upload: 0.51 KiB / gzip: 0.28 KiB
Uploaded my-worker (2.34 sec)
Published my-worker (0.89 sec)
  https://my-worker.YOUR-SUBDOMAIN.workers.dev
Your Worker is now live on Cloudflare’s global network across 300+ cities!
The first deployment will prompt you to log in to Cloudflare. Make sure you have a Cloudflare account (free tier available).

​
Understanding the Configuration

Your wrangler.jsonc file contains the Worker configuration:
wrangler.jsonc
{
  "$schema": "node_modules/wrangler/config-schema.json",
  "name": "my-worker",
  "main": "./src/index.ts",
  "compatibility_date": "2026-03-03"
}
  • name: Your Worker’s name (used in the deployment URL)
  • main: Entry point file for your Worker
  • compatibility_date: The version of the Workers runtime to use
  • $schema: Enables autocomplete in your editor
You can add bindings to KV, R2, D1, and other Cloudflare services:
wrangler.jsonc
{
  "name": "my-worker",
  "main": "./src/index.ts",
  "compatibility_date": "2026-03-03",
  "kv_namespaces": [
    { "binding": "MY_KV", "id": "your-kv-namespace-id" }
  ],
  "r2_buckets": [
    { "binding": "MY_BUCKET", "bucket_name": "my-bucket" }
  ]
}

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Next Steps

Now that you have your first Worker running, explore these topics:

Handle Requests

Learn to parse URLs, read headers, and handle different HTTP methods

Add Storage

Connect to KV for key-value storage or D1 for SQL databases

Use Bindings

Integrate with R2, Durable Objects, and other Cloudflare services

Write Tests

Test your Workers locally with Vitest and @cloudflare/vitest-pool-workers

​
Common Commands

Here are the most frequently used Wrangler commands:
CommandDescription
wrangler devStart local development server
wrangler deployDeploy to production
wrangler tailStream live logs from production
wrangler kv:namespace create <name>Create a KV namespace
wrangler d1 create <name>Create a D1 database
wrangler whoamiCheck authentication status
Run wrangler --help to see all available commands or wrangler <command> --help for specific command help.

​
Alternative: Using Wrangler Init

You can also create a Worker using Wrangler directly: 
npx wrangler init my-worker -y
This creates a minimal Worker setup without the interactive prompts.

​
Troubleshooting

If port 8787 is already in use, specify a different port:
wrangler dev --port 8788
If you have trouble authenticating:
  1. Run wrangler logout to clear credentials
  2. Run wrangler login to authenticate again
  3. Alternatively, use an API token with wrangler login --scopes-list
Make sure all dependencies are installed:
npm install
Need help? Join the Cloudflare Discord or check the GitHub Discussions.

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