Common Webhook Errors and How to Fix Them (2025 Guide)

Debug webhook failures like a pro. Complete troubleshooting guide for 404s, timeouts, signature errors, and more common webhook issues.

October 14, 2025
•
9 min read
•
By Josh, Founder

Common Webhook Errors and How to Fix Them (2025 Guide)

Webhooks fail. It's a fact of life when building integrations. Whether you're working with Stripe, Shopify, GitHub, or any other service, you'll eventually encounter webhook errors that leave you scratching your head.

After debugging thousands of webhook failures (and building WebhookDebugger to help others do the same), I've seen every error imaginable. Most webhook issues fall into predictable patterns with straightforward solutions.

This guide covers the 10 most common webhook errors, why they happen, and exactly how to fix them. By the end, you'll be able to debug webhook failures faster than most senior developers.

1. The Dreaded 404: Endpoint Not Found

Error: 404 Not Found

What it means: The webhook URL doesn't exist or is unreachable.

Common Causes:

  • Wrong URL: Copy-paste error in webhook configuration
  • Route not deployed: Code exists locally but not in production
  • Domain issues: Using wrong subdomain (www vs non-www)
  • Path typos: /api/webhooks vs /api/webhook

How to Fix:

  1. Verify the URL manually:

    curl -X POST https://yoursite.com/api/webhooks/endpoint

    Should return something other than 404.

  2. Check your deployment: Ensure the webhook route is deployed to production.

  3. Test domain variations:

    • Try with and without www
    • Check for https vs http
    • Verify no trailing slashes

  4. Review your routing: Make sure the path matches your code exactly.

2. Timeout Errors (504 Gateway Timeout)

Error: 504 Gateway Timeout or request timeout

What it means: Your webhook endpoint is taking too long to respond.

Common Causes:

  • Slow database queries: Webhook triggers complex database operations
  • External API calls: Webhook makes outbound requests that are slow
  • Cold starts: Serverless functions taking time to warm up
  • Infinite loops: Webhook accidentally triggers itself

How to Fix:

  1. Optimize database queries:

    // Bad: Multiple queries in webhook
app.post('/webhook', async (req, res) => {
  const user = await db.users.findOne({id: req.body.user_id});
  const order = await db.orders.create({...});
  const notification = await db.notifications.create({...});
  res.status(200).send('OK');
});

// Good: Single transaction or background job
app.post('/webhook', async (req, res) => {
  await queue.add('process-webhook', req.body);
  res.status(200).send('OK');
});

  2. Use background jobs: Process webhook data asynchronously

  3. Add timeouts: Set reasonable limits on external API calls

  4. Return 200 ASAP: Acknowledge receipt immediately, process later

3. Signature Verification Failures (401 Unauthorized)

Error: 401 Unauthorized or "Invalid signature"

What it means: Webhook signature doesn't match expected value.

Common Causes:

  • Wrong secret: Using test secret in production (or vice versa)
  • Body modification: Request body changed before verification
  • Encoding issues: Character encoding problems
  • Timing problems: Timestamp outside acceptable window

How to Fix:

  1. Verify your secret:

    // Check environment variables
console.log('Webhook secret:', process.env.WEBHOOK_SECRET?.slice(0, 10) + '...');

// For Stripe webhooks
const sig = req.headers['stripe-signature'];
const secret = process.env.STRIPE_WEBHOOK_SECRET;

  2. Log the raw body:

    // Debug signature verification
console.log('Raw body:', req.body);
console.log('Headers:', req.headers);
console.log('Computed signature:', computedSignature);
console.log('Received signature:', receivedSignature);

  3. Check middleware order: Verify signature BEFORE any body parsing

  4. Handle encoding: Ensure consistent UTF-8 encoding

4. The Silent Failure (200 OK but Nothing Happens)

Error: Webhook returns 200 but doesn't process data

What it means: Code runs without errors but doesn't do what you expect.

Common Causes:

  • Wrong event type: Filtering for events that never match
  • Data structure assumptions: Expecting fields that don't exist
  • Silent exceptions: Errors caught but not logged
  • Environment issues: Database not connected, API keys missing

How to Fix:

  1. Add comprehensive logging:

    app.post('/webhook', async (req, res) => {
  console.log('Webhook received:', {
    type: req.body.type,
    id: req.body.id,
    timestamp: new Date().toISOString()
  });
  
  try {
    // Process webhook
    console.log('Processing completed successfully');
  } catch (error) {
    console.error('Webhook processing failed:', error);
    // Still return 200 to prevent retries for invalid data
  }
  
  res.status(200).send('OK');
});

  2. Validate data structure: Check required fields exist before using them

  3. Test with real data: Use actual webhook payloads, not mock data

5. Rate Limiting (429 Too Many Requests)

Error: 429 Too Many Requests

What it means: You're receiving webhooks faster than you can process them.

Common Causes:

  • Webhook storms: Service sends many webhooks rapidly
  • Retry loops: Failed webhooks trigger infinite retries
  • No rate limiting: No protection against webhook floods

How to Fix:

  1. Implement rate limiting:

    const rateLimit = require('express-rate-limit');

const webhookLimiter = rateLimit({
  windowMs: 1 * 60 * 1000, // 1 minute
  max: 100, // 100 requests per minute
  message: 'Too many webhook requests'
});

app.use('/api/webhooks', webhookLimiter);

  2. Use queues: Buffer incoming webhooks in a queue

  3. Return errors correctly: Use 4xx for permanent failures, 5xx for retries

6. JSON Parsing Errors (400 Bad Request)

Error: 400 Bad Request or "Invalid JSON"

What it means: Request body isn't valid JSON or is corrupted.

Common Causes:

  • Content-Type mismatch: Expecting JSON but receiving form data
  • Character encoding: Non-UTF8 characters breaking JSON
  • Truncated requests: Large payloads getting cut off

How to Fix:

  1. Check Content-Type header:

    app.post('/webhook', (req, res) => {
  console.log('Content-Type:', req.headers['content-type']);
  
  if (req.headers['content-type'] !== 'application/json') {
    return res.status(400).send('Expected JSON');
  }
  
  // Process webhook
});

  2. Handle parsing errors gracefully:

    app.use('/webhook', express.raw({type: 'application/json'}));

app.post('/webhook', (req, res) => {
  let body;
  try {
    body = JSON.parse(req.body);
  } catch (error) {
    console.error('JSON parse error:', error);
    return res.status(400).send('Invalid JSON');
  }
  
  // Process parsed body
});

7. Database Connection Failures (500 Internal Server Error)

Error: 500 Internal Server Error

What it means: Your webhook code crashed due to infrastructure issues.

Common Causes:

  • Database timeouts: Connection pool exhausted
  • Environment variables: Missing database credentials
  • Cold starts: Database connections not initialized

How to Fix:

  1. Add connection retry logic:

    async function connectWithRetry() {
  const maxRetries = 3;
  for (let i = 0; i < maxRetries; i++) {
    try {
      await db.connect();
      return;
    } catch (error) {
      if (i === maxRetries - 1) throw error;
      await new Promise(resolve => setTimeout(resolve, 1000));
    }
  }
}

  2. Use connection pooling: Reuse database connections

  3. Health checks: Monitor database connectivity

8. Memory Leaks and Performance Issues

Error: Gradually degrading performance or crashes

What it means: Webhook handler has memory leaks or performance issues.

Common Causes:

  • Unclosed connections: Database or HTTP connections not properly closed
  • Large objects in memory: Processing massive webhook payloads
  • Event listener leaks: Adding listeners without removing them

How to Fix:

  1. Monitor memory usage:

    setInterval(() => {
  const used = process.memoryUsage();
  console.log('Memory usage:', {
    rss: Math.round(used.rss / 1024 / 1024) + ' MB',
    heapUsed: Math.round(used.heapUsed / 1024 / 1024) + ' MB'
  });
}, 30000);

  2. Use streaming for large payloads: Don't load entire webhook body into memory

  3. Clean up resources: Always close connections and remove listeners

9. SSL/TLS Certificate Issues

Error: SSL verification failed or certificate errors

What it means: HTTPS certificate problems preventing webhook delivery.

Common Causes:

  • Expired certificates: SSL certificate needs renewal
  • Self-signed certificates: Using invalid certificates in production
  • Certificate chain issues: Intermediate certificates missing

How to Fix:

  1. Check certificate validity:

    # Test SSL certificate
openssl s_client -connect yoursite.com:443 -servername yoursite.com

# Check expiration
echo | openssl s_client -connect yoursite.com:443 2>/dev/null | openssl x509 -noout -dates

  2. Use proper certificates: Let's Encrypt, Cloudflare, or commercial SSL

  3. Test with SSL Labs: https://www.ssllabs.com/ssltest/

10. Idempotency Issues (Duplicate Processing)

Error: Same webhook processed multiple times

What it means: Webhooks are being retried and processed as new events.

Common Causes:

  • No deduplication: Not tracking processed webhook IDs
  • Slow responses: Webhook takes too long, triggers retries
  • Transient failures: Temporary issues cause retries

How to Fix:

  1. Implement idempotency:

    const processedWebhooks = new Set();

app.post('/webhook', async (req, res) => {
  const webhookId = req.body.id;
  
  if (processedWebhooks.has(webhookId)) {
    console.log('Duplicate webhook ignored:', webhookId);
    return res.status(200).send('OK');
  }
  
  try {
    await processWebhook(req.body);
    processedWebhooks.add(webhookId);
  } catch (error) {
    console.error('Webhook processing failed:', error);
    return res.status(500).send('Error');
  }
  
  res.status(200).send('OK');
});

  2. Use database tracking: Store processed webhook IDs in database

  3. Return 200 quickly: Acknowledge receipt within 5 seconds

Debugging Tools and Techniques

Essential Debugging Tools:

  • WebhookDebugger: Real-time webhook inspection and history
  • Webhook.site: Simple webhook testing for quick debugging
  • ngrok: Expose local development server for webhook testing
  • Stripe CLI: Test Stripe webhooks locally
  • Postman: Replay webhook requests with different payloads

Debugging Checklist:

  1. Check the basics:

    • Is the URL accessible? (Test with curl)
    • Are environment variables set correctly?
    • Is the code deployed to production?

  2. Add logging:

    • Log incoming webhook data
    • Log processing steps
    • Log errors with full stack traces

  3. Test with real data:

    • Use actual webhook payloads from your service
    • Test edge cases (missing fields, large payloads)
    • Verify signature validation with real secrets

  4. Monitor in production:

    • Set up error tracking (Sentry, Rollbar)
    • Monitor response times and success rates
    • Track webhook processing metrics

Prevention is Better Than Debugging

The best webhook bugs are the ones that never happen. Here are some proactive measures:

  • Comprehensive testing: Test webhooks in staging environment before production
  • Graceful error handling: Always return appropriate HTTP status codes
  • Monitoring and alerting: Get notified when webhook success rates drop
  • Documentation: Document your webhook endpoints and expected payloads
  • Version your APIs: Use versioned webhook URLs to avoid breaking changes

Conclusion

Webhook debugging doesn't have to be a mystery. Most failures follow predictable patterns:

  • 404s are usually URL or deployment issues
  • Timeouts mean your code is too slow
  • 401s indicate signature verification problems
  • 500s point to infrastructure or code errors

Start with the basics (URL, credentials, deployment), add comprehensive logging, and use proper debugging tools. With these techniques, you'll resolve webhook issues in minutes instead of hours.

If you're tired of digging through server logs to debug webhook failures, try WebhookDebugger. It captures webhook requests in real-time, shows you exactly what's being sent, and helps you debug faster with a clean, developer-friendly interface.

Happy debugging!

Last updated: October 2025 | Written by Josh, Founder