10 Common n8n Errors and How to Fix Them

Even the best workflows encounter errors. This guide covers the most common n8n issues and their solutions, helping you debug faster and build more reliable automations.

1. "Workflow did not return any data"

Symptoms:

• Workflow executes without errors
• No output data in final node
• Empty results

Root Causes:

• No items passed to final node
• All items filtered out by IF/Switch node
• Empty API response

Solution: Check the "Input" tab of each node to see data flow. Add debug nodes (Set node) to inspect data at each step. Verify IF/Switch conditions aren't filtering all items.

// Check if data exists before processing
const items = $input.all();

if (items.length === 0) {
  return [{
    json: {
      warning: 'No data to process',
      timestamp: new Date().toISOString()
    }
  }];
}

return items;

2. "Workflow execution timed out"

Symptoms:

• Workflow stops after X minutes
• Error: "Execution timed out"
• Incomplete processing

Root Causes:

• Long-running operations
• API calls with no response
• Infinite loops in Code nodes
• Default timeout too short

Solution: Increase the timeout in your n8n settings:

EXECUTIONS_TIMEOUT=3600  # 1 hour in seconds
EXECUTIONS_TIMEOUT_MAX=7200  # Max 2 hours

For large datasets, break processing into batches using the Split In Batches node.

3. "Authentication failed"

Symptoms:

• Error: "401 Unauthorized"
• Credentials not working
• API returns authentication error

Root Causes:

• Expired tokens
• Wrong credentials
• Missing permissions

Solution:

1. Re-authenticate in credential settings
2. Check if API key has required scopes
3. Verify OAuth tokens haven't expired
4. Test credentials with a simple API call first

4. "Rate limit exceeded"

Symptoms:

• Error: "429 Too Many Requests"
• Workflow fails intermittently
• API returns rate limit error

Solution: Add delays between requests:

// Add 1 second delay between items
await new Promise(r => setTimeout(r, 1000));

Or use the "Split In Batches" node with "Wait Between Batches" option.

5. "Expression evaluation failed"

Symptoms:

• Red error in expression field
• "Cannot read property 'x' of undefined"
• Workflow won't execute

Root Causes:

• Missing data in expected field
• Typo in field name
• Data structure changed

Solution: Use optional chaining and fallbacks:

// Instead of this (breaks if field missing):
{{ $json.customer.email }}

// Use this (safe access):
{{ $json.customer?.email ?? 'no-email@example.com' }}

6. "Webhook not receiving data"

Symptoms:

• Webhook URL works in testing
• No data when triggered externally
• Timeout on webhook wait

Root Causes:

• Firewall blocking requests
• Wrong webhook path
• HTTP vs HTTPS mismatch

Solution:

1. Verify webhook URL is publicly accessible
2. Check firewall/network settings
3. Use n8n's test webhook URL first
4. Ensure sender uses correct HTTP method (GET/POST)

7. "Data transformation returns wrong format"

Symptoms:

• Output structure unexpected
• Missing fields after transformation
• Array instead of object (or vice versa)

Solution: Always verify your data structure:

// Log data structure for debugging
console.log(JSON.stringify($input.all(), null, 2));

// Return properly formatted data
return $input.all().map(item => ({
  json: {
    id: item.json.id,
    name: item.json.name || 'Unknown',
    email: item.json.email?.toLowerCase()
  }
}));

8. "Cannot connect to database"

Symptoms:

• Database node fails
• Connection timeout
• Authentication error

Root Causes:

• Wrong connection string
• Database not accessible from n8n server
• SSL requirements

Solution:

1. Test connection string with a database client
2. Ensure n8n server can reach database (check IP whitelist)
3. Enable/disable SSL as required by database
4. Verify port is correct (MySQL: 3306, PostgreSQL: 5432)

9. "Workflow loops forever"

Symptoms:

• Workflow never completes
• Memory usage increases
• Thousands of executions

Root Causes:

• Webhook triggers itself
• Infinite recursion in logic
• No exit condition

Solution: Add exit conditions and self-trigger prevention:

// Prevent infinite loops
if ($json.processedCount > 100) {
  return []; // Stop processing
}

// Mark items as processed
return [{
  json: {
    ...item.json,
    processedCount: ($json.processedCount || 0) + 1
  }
}];

10. "Memory limit exceeded"

Symptoms:

• Error: "Heap out of memory"
• Workflow crashes with large datasets
• Node.js memory error

Solution: Process data in chunks:

1. Use "Split In Batches" node (process 50-100 items at a time)
2. Stream large files instead of loading entirely
3. Increase memory limit: NODE_OPTIONS="--max-old-space-size=4096"
4. Offload heavy processing to external services

Debugging Best Practices

1. Check execution logs - Review the output of each node
2. Use console.log - Add logging in Code nodes
3. Test incrementally - Verify each node works before adding more
4. Pin data - Use pinned data to test without hitting APIs
5. Read error messages - n8n errors usually indicate the exact issue

Conclusion

Most n8n errors fall into predictable categories: authentication, data structure, timing, or resource limits. By understanding these common patterns, you can quickly diagnose and fix issues in your workflows.

Want to master n8n debugging? Our courses include dedicated troubleshooting sections and best practices for building reliable automations.