HTTP Status Code Reference
Complete interactive reference for every HTTP response status code. Search by number or keyword, filter by category, and understand the technical meaning, use cases, and developer implications of each code.
Understanding HTTP Response Categories
HTTP status codes follow a structured numbering system defined by the IETF (Internet Engineering Task Force) in RFC 9110. The first digit indicates the response category, while the remaining two digits specify the exact condition.
- 1xx: Request received, server is continuing to process.
- 2xx: Request successfully received, understood, and accepted.
- 3xx: Further action needed to complete the request (redirect).
- 4xx: Request contains bad syntax or cannot be fulfilled (client fault).
- 5xx: Server failed to fulfill a valid request (server fault).
Most Common Status Codes for Developers
- 200 OK — Standard success response for GET and POST requests.
- 201 Created — Resource was successfully created (POST/PUT).
- 301 Moved Permanently — Permanent URL redirect, passes SEO equity.
- 400 Bad Request — Malformed request syntax or invalid parameters.
- 401 Unauthorized — Authentication required or credentials invalid.
- 404 Not Found — Resource does not exist at the requested URL.
- 500 Internal Server Error — Generic server-side failure.
Frequently Asked Questions
What are HTTP status codes?
HTTP status codes are standardized three-digit response codes returned by web servers to indicate the result of a client request. They are grouped into five classes: 1xx (Informational), 2xx (Success), 3xx (Redirection), 4xx (Client Error), and 5xx (Server Error). Understanding these codes is essential for debugging API integrations and web applications.
What is the difference between 301 and 302 redirects?
A 301 redirect signals a permanent move — search engines transfer all ranking signals to the new URL. A 302 redirect is temporary — search engines keep the original URL indexed. Use 301 for domain migrations and URL restructuring, and 302 for temporary maintenance pages or A/B testing redirects.
What does a 403 Forbidden status mean?
A 403 Forbidden response means the server understood the request but refuses to authorize it. Unlike 401 (Unauthorized), re-authenticating will not help. Common causes include IP blocking, file permission restrictions, directory listing disabled, or Web Application Firewall (WAF) rules blocking the request.
When should I return a 204 No Content response?
Return 204 when a request was processed successfully but there is no response body to send back. This is ideal for DELETE operations, form submissions that should not navigate away, or CORS preflight responses where only headers matter.
- Status code definitions follow RFC 9110 (HTTP Semantics) and RFC 6585 (Additional HTTP Status Codes).
- Search is instant — filtering operates on a pre-built in-memory index with zero network requests.
- Some codes (like 418 I'm a teapot) are included as historically notable standards humor.