What do the HTTP status code classes mean?

1xx are informational, 2xx mean success, 3xx are redirects, 4xx are client errors (the request was wrong), and 5xx are server errors (the server failed to fulfil a valid request).

What is the difference between 401 and 403?

401 Unauthorized means authentication is missing or failed, so logging in may fix it. 403 Forbidden means the server understood who you are but still refuses access, so credentials will not help.

Is anything I search sent to a server?

No. The entire reference and search runs entirely in your browser — nothing you type is uploaded anywhere.

HTTP Status Codes Reference

Every HTTP status code with its meaning — searchable and instant.

HTTP status codes — searchable reference

A complete, searchable list of the HTTP status codes you actually hit while building and debugging APIs: 200 OK, 301 Moved Permanently, 404 Not Found, 429 Too Many Requests, 500 Internal Server Error and more — each grouped by class with a plain-English meaning.

Search by number, name, or meaning to find the right code instantly. Everything runs in your browser; nothing is uploaded.