Cloudflare Workers Playground Skill Reference

Overview

Cloudflare Workers Playground is a browser-based sandbox for instantly experimenting with, testing, and deploying Cloudflare Workers without authentication or setup. This skill provides patterns, APIs, and best practices specifically for Workers Playground development.

URL: workers.cloudflare.com/playground

⚠️ Playground Constraints

Playground is NOT production-equivalent:

• ✅ Real Workers runtime, instant testing, shareable URLs
• ❌ No TypeScript (JavaScript only)
• ❌ No bindings (KV, D1, R2, Durable Objects)
• ❌ No environment variables or secrets
• ❌ ES modules only (no Service Worker format)
• ⚠️ Safari broken (use Chrome/Firefox)

For production: Use wrangler CLI. Playground is for rapid prototyping.

Quick Start

Minimal Worker:

  async fetch(request, env, ctx) {
    return new Response('Hello World');
  }
};

JSON API:

  async fetch(request, env, ctx) {
    const data = { message: 'Hello', timestamp: Date.now() };
    return Response.json(data);
  }
};

Proxy with modification:

  async fetch(request, env, ctx) {
    const response = await fetch('https://example.com');
    const modified = new Response(response.body, response);
    modified.headers.set('X-Custom-Header', 'added-by-worker');
    return modified;
  }
};

Import from CDN:

  async fetch(request) {
    const app = new Hono();
    app.get('/', (c) => c.text('Hello Hono!'));
    return app.fetch(request);
  }
};

Reading Order

1. configuration.md - Start here: playground setup, constraints, deployment
2. api.md - Core APIs: Request, Response, ExecutionContext, fetch, Cache
3. patterns.md - Common use cases: routing, proxying, A/B testing, multi-module code
4. gotchas.md - Troubleshooting: errors, browser issues, limits, best practices

In This Reference

• configuration.md - Setup, deployment, configuration
• api.md - API endpoints, methods, interfaces
• patterns.md - Common patterns, use cases, examples
• gotchas.md - Troubleshooting, best practices, limitations

Key Features

No Setup Required:

• Open URL and start coding
• No CLI, no account, no config files
• Code executes in real Cloudflare Workers runtime

Instant Preview:

• Live preview pane with browser tab or HTTP tester
• Auto-reload on code changes
• DevTools integration (right-click → Inspect)

Share & Deploy:

• Copy Link generates permanent shareable URL
• Deploy button publishes to production in ~30 seconds
• Get *.workers.dev subdomain immediately

Common Use Cases

• API development: Test endpoints before wrangler setup
• Learning Workers: Experiment with APIs without local environment
• Prototyping: Quick POCs for edge logic
• Sharing examples: Generate shareable links for bug reports or demos
• Framework testing: Import from CDN (Hono, itty-router, etc.)

Limitations vs Production

See Also

• Cloudflare Workers Docs
• Workers Examples
• Wrangler CLI
• Workers API Reference