The HTTP status code lookup lets you instantly search and understand any HTTP response code. Type a code number (like 404) or a keyword (like "redirect" or "timeout") to see the code's meaning, common causes, and when to use it. Covers all 1xx–5xx codes from RFC 7231 and common extensions.
Common Causes
Response Headers (Example)
No matching status codes found
How to Use the HTTP Status Code Lookup
HTTP status codes are 3-digit numbers returned by web servers in response to browser requests. They tell the client whether the request succeeded, failed, needs authentication, or has been redirected. This HTTP status code lookup tool covers all standard codes from RFC 7231, plus commonly used extensions like 429 Too Many Requests and 451 Unavailable For Legal Reasons.
Searching for a Status Code
Type a code number (like 404), a phrase fragment (like Not Found), or a keyword related to the behavior (like redirect, auth, or timeout). The results update live as you type. Click any code card to see a full explanation with common causes and response header examples.
Understanding the Five Categories
1xx Informational — Request received, continuing process. Rarely seen in browser DevTools. 2xx Success — Request successfully received, understood, and accepted. 3xx Redirection — Further action needed to complete the request (follow the Location header). 4xx Client Error — Request contains bad syntax or cannot be fulfilled (client's fault). 5xx Server Error — Server failed to fulfill a valid request (server's fault).
Choosing the Right Status Code for Your API
For REST API design: return 200 OK for successful GET/PUT/PATCH requests, 201 Created for successful POST that creates a resource, 204 No Content for successful DELETE, 400 for malformed requests, 401 for unauthenticated requests, 403 for unauthorized (authenticated but no permission), 404 for missing resources, 429 for rate limiting, and 500 for unexpected server errors.
Debugging HTTP Errors
When debugging, look at the status code first to understand what category of problem occurred. A 4xx error means the client (your code or the API caller) sent a bad request — check the request headers, body format, and authentication. A 5xx error means the server is having problems — check server logs, upstream dependencies, and resource usage. A 3xx redirect loop usually means the redirect destination also redirects, creating a cycle.
FAQ
Is this HTTP status code lookup free?
Yes, completely free with instant search. No account required. All data is embedded in the page — search works offline once loaded.
What is the difference between 401 and 403?
401 Unauthorized means the client is not authenticated — they need to log in or provide credentials. 403 Forbidden means the client IS authenticated but lacks permission to access the resource. Use 401 for missing/invalid credentials, 403 for insufficient permissions.
When should I use 422 vs 400 for validation errors?
400 Bad Request is for malformed syntax (invalid JSON, missing required headers). 422 Unprocessable Entity is for semantically invalid requests (valid JSON but invalid field values like negative age). Many REST APIs use 400 for both — consistency matters more than strict interpretation.
What is the difference between 301 and 302 redirects?
301 Moved Permanently means the resource has permanently moved — browsers cache it and search engines transfer link equity to the new URL. 302 Found is a temporary redirect — browsers don't cache it and search engines keep the original URL in index.
What HTTP status codes should I return for REST API errors?
400 for malformed requests, 401 for missing authentication, 403 for insufficient permissions, 404 for resources not found, 409 for conflicts (e.g., duplicate), 422 for validation errors, 429 for rate limiting, 500 for server errors. Avoid 200 OK with an error body in the JSON — use proper status codes.
What does the 5xx range of status codes mean?
5xx codes indicate server-side errors. 500 Internal Server Error is a generic catch-all for unexpected failures. 502 Bad Gateway means an upstream server returned an invalid response. 503 Service Unavailable means the server is temporarily down (maintenance or overload). 504 Gateway Timeout means an upstream server took too long to respond.