HTTP Status Code Lookup

HTTP status codes are three-digit numbers that indicate the result of an HTTP request. The first digit defines the category: 1xx (Informational), 2xx (Success), 3xx (Redirection), 4xx (Client Error), 5xx (Server Error). Each code has a standard reason phrase (e.g., 404 Not Found) and specific semantics. Understanding these codes helps developers debug API issues, configure proper error handling, and improve user experience.

This tool provides a searchable reference of all standard HTTP status codes. Enter any code from 100 to 599 to see its meaning, common causes, and how to fix it. Use the quick filter buttons to browse by category.

The most common errors developers encounter: 400 Bad Request (malformed request — validate your JSON and parameters), 401 Unauthorized (missing or invalid credentials — add Authorization header), 403 Forbidden (insufficient permissions — check access control), 404 Not Found (resource doesn't exist — verify URL), 422 Unprocessable Content (validation failed — check response body for details), 429 Too Many Requests (rate limited — wait and retry), 500 Internal Server Error (server bug — check logs). Each has specific causes and remediation steps.

For 4xx errors, the fix is usually on the client side. For 5xx errors, the fix is on the server side. Use this lookup to quickly identify the issue and apply the correct fix.

Use the correct status code for your API responses. 200 for successful GET, 201 for successful POST that creates a resource, 204 for successful DELETE with no body. Use 301 for permanent redirects, 302/307 for temporary. Return 400 for client mistakes, 401 for auth required, 403 for forbidden, 404 for not found. Use 422 for validation errors (semantic failures). Return 500 only for unexpected server errors; use 502/503/504 for gateway and availability issues.

Include helpful error messages in the response body. For rate limiting (429), send Retry-After. For maintenance (503), send Retry-After. Link to detailed documentation when possible. Consistent status code usage makes APIs predictable and easier to debug.