HTTP Status Code Lookup

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A complete reference of HTTP status codes from 100 to 599 with explanations, typical causes, related headers and QA testing hints. Search by number, name or class.

Privacy: This tool runs entirely in your browser. Your input never leaves your device.

How to use HTTP Status Code Lookup

  1. Type a status code (429), a class (5xx) or a keyword such as "conflict".
  2. Read the detail card for the meaning, RFC reference, usage guidance and testing hint.
  3. Use the class filter or untick non-standard codes to narrow the table.
  4. Copy or download the table as CSV for test plans and documentation.

HTTP Status Code Lookup features

  • Every IANA-registered status code from 100 to 511 with meaning, RFC 9110 section and typical causes
  • Widely used non-standard codes (Cloudflare 52x, Nginx 444/499, AWS ELB 460/463, Laravel 419) clearly marked
  • Search by exact number, class (4xx), partial number (50) or keyword ("rate limit", "redirect")
  • QA hints: what to test, which headers to assert, whether a retry is safe and whether the response is cacheable
  • Unassigned codes explained by class semantics instead of returning nothing
  • Filter by class and hide vendor codes when you only want the standard

HTTP Status Code Lookup example

Look up 429

Input:

429

Output:

429 Too Many Requests — 4xx Client Error
RFC 6585 §4
When to use: API throttling per key, per IP or per user.
Testing hint: burst requests above the limit; verify Retry-After and X-RateLimit-* headers.
Retry safe? Yes — with backoff (honour Retry-After)

Frequently asked questions about HTTP Status Code Lookup

What is the difference between 401 and 403?

401 Unauthorized means the request has no valid credentials (missing, expired or wrong token) and must include a WWW-Authenticate challenge. 403 Forbidden means the client is authenticated but is not allowed to perform the action. Re-authenticating fixes a 401; it never fixes a 403.

Should I use 301 or 308 for a permanent redirect?

Both are permanent. 301 lets clients change a POST into a GET, while 308 guarantees the method and body are preserved. Use 301 for pages and 308 for API endpoints that receive non-GET requests.

Which status codes are safe to retry automatically?

429, 502, 503, 504 and 408 are transient and can be retried with exponential backoff (honour Retry-After). 4xx codes other than 408/429 indicate a client problem and should not be retried unchanged.

Are Cloudflare 52x codes real HTTP codes?

They are not registered with IANA. Cloudflare returns 520–530 to describe problems between its edge and your origin. The tool lists them, marked as non-standard, so you can diagnose them quickly.

What does an unassigned code such as 499 mean?

Clients must treat unknown codes as the x00 code of their class (e.g. 499 behaves like 400). Nginx uses 499 in its logs for "client closed request". The lookup explains such vendor uses where they exist.

Technical notes

The reference follows RFC 9110 (HTTP Semantics, 2022), which obsoleted RFC 7231 and renamed a few codes (413 Content Too Large, 422 Unprocessable Content). WebDAV, RFC 6585 and RFC 8297 codes are included with their own references.

Cacheability follows the RFC 9110 list of heuristically cacheable codes (200, 203, 204, 206, 300, 301, 308, 404, 405, 410, 414, 501); any other code requires explicit Cache-Control directives to be stored.