Look up an HTTP status code and see its common reason phrase plus a short explanation useful when debugging browsers, APIs, and reverse proxies.
How it works
Enter an integer from 100 to 599. Codes present in the built-in table—covering everyday successes (2xx), redirects (3xx), client errors (4xx), and server errors (5xx), including a few less common but widely used values such as 418, 422, and 429—return the phrase and description. Codes outside 100–599 are invalid; codes inside the range but absent from the table return unknown-status so you know the number is legal HTTP space but not documented here.
When to use it
- Decode a failing fetch or curl response without leaving the page
- Confirm whether 301 vs 308 preserves the request method in redirects
- Teach juniors what 401 vs 403 means during an auth review
Limitations
The table is curated, not exhaustive of every IANA registration or proprietary extension. Reason phrases can vary by server; treat the output as guidance. Application-specific payloads in the response body are not interpreted.
Example
Code 404 resolves to reason phrase Not Found with a note that the target resource was not found. Code 99 is rejected as invalid; code 499 (sometimes used by nginx for client-closed requests) returns unknown-status in this lookup.