HTTP Error Codes Reference
Complete HTTP status codes reference. Client errors (4xx), server errors (5xx), success codes (2xx). Understand causes and fixes for common errors.
Success Codes (2xx)
200 OK: Request successful
201 Created: Resource created successfully
202 Accepted: Request accepted for processing
204 No Content: Success, no response body
206 Partial Content: Partial response delivered
Client Errors (4xx)
400 Bad Request: Invalid request syntax
Fix: Check request format, parameters
401 Unauthorized: Authentication required
Fix: Add authentication header, check credentials
403 Forbidden: Access denied
Fix: Check permissions, API key, user role
404 Not Found: Resource does not exist
Fix: Check URL, endpoint, resource ID
405 Method Not Allowed: HTTP method not supported
Fix: Use correct method (GET, POST, PUT)
406 Not Acceptable: Content type not acceptable
Fix: Check Accept header format
408 Request Timeout: Server timed out
Fix: Reduce request size, retry
409 Conflict: Resource state conflict
Fix: Check version, resolve conflict
410 Gone: Resource permanently removed
Fix: Use different resource, update link
413 Payload Too Large: Request body exceeds limit
Fix: Reduce upload size
414 URI Too Long: URL exceeds length limit
Fix: Shorten URL, use POST
415 Unsupported Media Type: Content format unsupported
Fix: Check Content-Type header
429 Too Many Requests: Rate limit exceeded
Fix: Wait, implement throttling
Server Errors (5xx)
500 Internal Server Error: Server error
Fix: Check server logs, contact admin
501 Not Implemented: Feature not supported
Fix: Server needs update
502 Bad Gateway: Proxy/gateway error
Fix: Check upstream server
503 Service Unavailable: Server overloaded/down
Fix: Wait, retry later
504 Gateway Timeout: Upstream server timeout
Fix: Check backend response time
505 HTTP Version Not Supported: HTTP version unsupported
Fix: Use HTTP/1.1 or HTTP/2
Common Error Troubleshooting
401: Check API key, OAuth token, session. 403: Verify permissions, CORS, IP restrictions. 404: Confirm endpoint URL exists. 500: Check server logs, database connection. 503: Server may be in maintenance, overloaded. Use DevTools Network panel for debugging.
Status Code Categories
1xx
Informational
Informational
2xx
Success
Success
3xx
Redirect
Redirect
4xx/5xx
Error
Error