# Interactive login (opens browser)
wrangler login

# Check auth status
wrangler whoami

# Use API token (CI/CD)
export CLOUDFLARE_API_TOKEN="your-token"

Reading Logs for Debugging

Tail Live Logs

# Stream logs from production
wrangler tail

# Stream logs from specific environment
wrangler tail --env staging

# Filter by status
wrangler tail --status error

# Filter by search term
wrangler tail --search "user-123"

# Filter by IP
wrangler tail --ip 192.168.1.1

# JSON output for parsing
wrangler tail --format json

Log Output Format

GET https://example.com/api/users - Ok @ 1/17/2026, 10:30:00 AM
  (log) Processing request for user-123
  (error) Database connection failed

Adding Console Logs

// Workers log to wrangler tail
export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    console.log('Request received:', request.url)
    console.log('Headers:', Object.fromEntries(request.headers))

    try {
      const result = await doSomething()
      console.log('Result:', JSON.stringify(result))
      return Response.json(result)
    } catch (error) {
      console.error('Error:', error.message, error.stack)
      return Response.json({ error: 'Internal error' }, { status: 500 })
    }
  }
}

Debugging Tips

Always log request context first

console.log(`[${request.method}] ${new URL(request.url).pathname}`)

Log before and after async operations

console.log('Fetching from KV...')
const value = await env.MY_KV.get(key)
console.log('KV result:', value ? 'found' : 'not found')

Use structured logging

console.log(JSON.stringify({
  type: 'request',
  path: url.pathname,
  method: request.method,
  timestamp: Date.now()
}))

Deployment

Deploy Worker

# Deploy to production
wrangler deploy

# Deploy to specific environment
wrangler deploy --env staging

# Dry run (see what would be deployed)
wrangler deploy --dry-run

# Deploy specific script
wrangler deploy src/worker.ts

Deploy Pages

# Deploy to Pages
wrangler pages deploy ./dist

# Deploy with specific project
wrangler pages deploy ./dist --project-name=my-site

# Deploy to specific branch
wrangler pages deploy ./dist --branch=preview

Configuration

wrangler.toml

name = "my-worker"
main = "src/index.ts"
compatibility_date = "2026-01-17"

# Environment variables (non-secret)
[vars]
API_URL = "https://api.example.com"
NODE_ENV = "production"

# KV Namespaces
[[kv_namespaces]]
binding = "MY_KV"
id = "abc123"

# D1 Databases
[[d1_databases]]
binding = "DB"
database_name = "my-database"
database_id = "def456"

# R2 Buckets
[[r2_buckets]]
binding = "BUCKET"
bucket_name = "my-bucket"

# Durable Objects
[[durable_objects.bindings]]
name = "MY_DO"
class_name = "MyDurableObject"

# Staging environment
[env.staging]
name = "my-worker-staging"
vars = { API_URL = "https://staging-api.example.com" }

[[env.staging.kv_namespaces]]
binding = "MY_KV"
id = "staging-kv-id"

Secrets

# Add secret (interactive)
wrangler secret put MY_SECRET

# Add secret from stdin
echo "secret-value" | wrangler secret put MY_SECRET

# Add to specific environment
wrangler secret put MY_SECRET --env staging

# List secrets
wrangler secret list

# Delete secret
wrangler secret delete MY_SECRET

Common Errors

"No account id found"

Error: No account id found, quitting...

Fix: Add account_id to wrangler.toml or login:

wrangler login
# or
wrangler whoami  # to verify auth

# wrangler.toml
account_id = "your-account-id"

"Worker not found"

Error: worker not found

Fix: Check worker name matches wrangler.toml:

# List all workers
wrangler deployments list

# Check wrangler.toml name field

"KV namespace not found"

Error: namespace not found

Fix: Create the namespace first:

# Create KV namespace
wrangler kv:namespace create MY_KV

# Use the returned id in wrangler.toml

"Script too large"

Error: Script startup exceeded CPU time limit

Fix:

Bundle size limit is 10MB (25MB on paid)
Check for large dependencies
Use dynamic imports for rarely-used code

# Check bundle size
wrangler deploy --dry-run --outdir=./dist
ls -la ./dist

"Binding not found"

Error: Cannot find binding "MY_KV"

Fix: Ensure binding is in wrangler.toml and matches code:

// Code expects env.MY_KV
interface Env {
  MY_KV: KVNamespace  // Must match wrangler.toml binding
}

KV Storage

# Create namespace
wrangler kv:namespace create MY_KV

# List namespaces
wrangler kv:namespace list

# Put value
wrangler kv:key put --binding=MY_KV "my-key" "my-value"

# Get value
wrangler kv:key get --binding=MY_KV "my-key"

# List keys
wrangler kv:key list --binding=MY_KV

# Delete key
wrangler kv:key delete --binding=MY_KV "my-key"

# Bulk upload
wrangler kv:bulk put --binding=MY_KV data.json

D1 Database

# Create database
wrangler d1 create my-database

# Execute SQL
wrangler d1 execute my-database --command="SELECT * FROM users"

# Execute SQL file
wrangler d1 execute my-database --file=./schema.sql

# Export database
wrangler d1 export my-database --output=backup.sql

# List databases
wrangler d1 list

R2 Storage

# Create bucket
wrangler r2 bucket create my-bucket

# List buckets
wrangler r2 bucket list

# Upload file
wrangler r2 object put my-bucket/path/file.txt --file=./local-file.txt

# Download file
wrangler r2 object get my-bucket/path/file.txt

# Delete file
wrangler r2 object delete my-bucket/path/file.txt

Local Development

# Start local dev server
wrangler dev

# Dev with specific port
wrangler dev --port 8787

# Dev with local mode (no network to Cloudflare)
wrangler dev --local

# Dev with specific environment
wrangler dev --env staging

# Dev with live reload
wrangler dev --live-reload

CI/CD with GitHub Actions

name: Deploy to Cloudflare

on:
  push:
    branches: [main]

jobs:
  deploy:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Setup Node
        uses: actions/setup-node@v4
        with:
          node-version: '20'

      - name: Install dependencies
        run: npm ci

      - name: Deploy Worker
        run: npx wrangler deploy
        env:
          CLOUDFLARE_API_TOKEN: ${{ secrets.CLOUDFLARE_API_TOKEN }}

Required Secrets

Secret	Description
`CLOUDFLARE_API_TOKEN`	API token with Workers edit permission
`CLOUDFLARE_ACCOUNT_ID`	Optional, can be in wrangler.toml

Debugging Checklist

When a worker fails:

Check live logs
```
wrangler tail --status error
```
Check recent deployments
```
wrangler deployments list
```
Rollback if needed
```
wrangler rollback
```
Test locally
```
wrangler dev
```

Check bindings

wrangler kv:namespace list
wrangler d1 list
wrangler r2 bucket list

Verify secrets
```
wrangler secret list
```

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Wrangler CLI

Installation

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