---

name: workers-dev-experience description: Cloudflare Workers local development with Wrangler, Miniflare, hot reload, debugging. Use for project setup, wrangler.jsonc configuration, or encountering local dev, HMR, binding simulation errors.

Cloudflare Workers Developer Experience

Local development setup with Wrangler, Miniflare, and modern tooling.

Quick Start

Copy# Create new project
bunx create-cloudflare@latest my-worker

# Or from scratch
mkdir my-worker && cd my-worker
bun init -y
bun add -d wrangler @cloudflare/workers-types

# Start local development
bunx wrangler dev

Essential wrangler.jsonc

Copy{
  "$schema": "node_modules/wrangler/config-schema.json",
  "name": "my-worker",
  "main": "src/index.ts",
  "compatibility_date": "2024-12-01",

  // Development settings
  "dev": {
    "port": 8787,
    "local_protocol": "http"
  },

  // Environment variables (non-secret)
  "vars": {
    "ENVIRONMENT": "development"
  },

  // Bindings
  "kv_namespaces": [
    { "binding": "KV", "id": "abc123", "preview_id": "def456" }
  ],

  "d1_databases": [
    { "binding": "DB", "database_id": "xyz789", "database_name": "my-db" }
  ],

  "r2_buckets": [
    { "binding": "BUCKET", "bucket_name": "my-bucket" }
  ]
}

Critical Rules

1. Always use wrangler dev for local testing - Simulates Cloudflare runtime accurately
2. Set compatibility_date - Controls runtime behavior, update quarterly
3. Use preview IDs for local dev - Separate from production bindings
4. Configure TypeScript properly - Use @cloudflare/workers-types
5. Enable source maps - Better error stacks in development

Top 6 Errors Prevented

Local Development Workflow

Copy# Start dev server (recommended)
bunx wrangler dev

# With live reload
bunx wrangler dev --live-reload

# Remote mode (use actual Cloudflare services)
bunx wrangler dev --remote

# Specify environment
bunx wrangler dev --env staging

# Custom port
bunx wrangler dev --port 3000

TypeScript Configuration

tsconfig.json:

Copy{
  "compilerOptions": {
    "target": "ES2022",
    "module": "ES2022",
    "moduleResolution": "bundler",
    "lib": ["ES2022"],
    "types": ["@cloudflare/workers-types"],
    "strict": true,
    "noEmit": true,
    "skipLibCheck": true,
    "allowSyntheticDefaultImports": true,
    "forceConsistentCasingInFileNames": true
  },
  "include": ["src/**/*"],
  "exclude": ["node_modules"]
}

Package.json Scripts

Copy{
  "scripts": {
    "dev": "wrangler dev",
    "deploy": "wrangler deploy",
    "deploy:staging": "wrangler deploy --env staging",
    "deploy:production": "wrangler deploy --env production",
    "test": "vitest",
    "test:watch": "vitest --watch",
    "type-check": "tsc --noEmit",
    "lint": "eslint src/",
    "types": "wrangler types",
    "tail": "wrangler tail",
    "db:migrate": "wrangler d1 migrations apply DB",
    "db:studio": "wrangler d1 execute DB --local --command 'SELECT 1'"
  }
}

Debugging

Console Logging

Copy// Development-only logging
export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    if (env.ENVIRONMENT === 'development') {
      console.log('Request:', request.method, request.url);
      console.log('Headers:', Object.fromEntries(request.headers));
    }

    // Handler logic...
  }
};

Using wrangler tail

Copy# Real-time logs from deployed worker
wrangler tail

# Filter by status
wrangler tail --status error

# Filter by method
wrangler tail --method POST

# JSON format for parsing
wrangler tail --format json

VS Code Debugging

.vscode/launch.json:

Copy{
  "version": "0.2.0",
  "configurations": [
    {
      "name": "Wrangler Dev",
      "type": "node",
      "request": "launch",
      "runtimeExecutable": "bunx",
      "runtimeArgs": ["wrangler", "dev", "--inspector-port", "9229"],
      "skipFiles": ["<node_internals>/**"],
      "sourceMaps": true
    }
  ]
}

When to Load References

Load specific references based on the task:

• Setting up project? → Load references/local-development.md for complete setup guide
• Configuring wrangler? → Load references/wrangler-config.md for all configuration options
• Debugging issues? → Load references/debugging-tools.md for debugging techniques

Templates

Scripts

Resources

• Wrangler CLI: https://developers.cloudflare.com/workers/wrangler/
• Configuration: https://developers.cloudflare.com/workers/wrangler/configuration/
• Local Development: https://developers.cloudflare.com/workers/testing/local-development/