HTTP Status Code Reference

How to use the http status code reference

1. Search by number, name or description.
2. Filter by class if you are exploring.
3. Read the practical note as well as the definition.

About this tool

Status codes are grouped by their first digit: 2xx succeeded, 3xx redirects, 4xx blames the request, 5xx blames the server. That split alone answers most questions — a 4xx means retrying unchanged will not help, a 5xx means it might.

Each entry here gives the specification meaning and, where it differs, what the code tends to mean in practice. 401 is the clearest example: it is named Unauthorized but actually means unauthenticated, and 403 is the one for a known user who is not allowed.

A few distinctions save real time. 301 versus 302 decides whether search engines transfer ranking, and browsers cache 301 aggressively enough that a mistaken one is painful to undo. 503 rather than 500 during maintenance tells search engines to come back rather than drop the page.

Common uses

• Working out what an API's error code means.
• Choosing the right code to return from your own endpoint.
• Explaining a 502 or 504 to someone else.

Frequently asked questions

What is the difference between 401 and 403?

401 means you are not authenticated — log in and retry. 403 means you are authenticated and still not allowed, so retrying will not help.

Should I use 301 or 302?

301 for permanent moves, which passes ranking signals and is cached hard by browsers. 302 for temporary ones.

What is the difference between 502 and 504?

502 means an upstream server gave an invalid response, often because it crashed. 504 means it did not respond in time.