Overview
What this reference is
A searchable, filterable list of the HTTP status codes you'll actually encounter, with their names and plain-English meanings. Search by code or keyword, filter by class, and copy a code with one click. It runs entirely in your browser.
What the first digit means
The five classes
Every status code is three digits, and the first digit tells you the category:
| Class | Meaning | |
|---|---|---|
| 1xx | Informational | Request received, continuing |
| 2xx | Success | The request worked |
| 3xx | Redirection | Further action needed (usually a redirect) |
| 4xx | Client error | The request was wrong (your side) |
| 5xx | Server error | The server failed (their side) |
Everyday status codes
The codes you'll use most
- 200 OK — the standard success response
- 201 Created — a new resource was made (after POST)
- 301 Moved Permanently — permanent redirect, passes SEO value
- 302 Found — temporary redirect
- 304 Not Modified — use your cached copy
- 400 Bad Request — malformed request
- 401 Unauthorized — you need to log in
- 403 Forbidden — you're logged in but not allowed
- 404 Not Found — the resource doesn't exist
- 429 Too Many Requests — you're being rate-limited
- 500 Internal Server Error — generic server failure
- 503 Service Unavailable — temporarily down or overloaded
Get this right
301 vs 302: the SEO one
Permanent vs temporary redirects
301 when a page has permanently moved — search engines transfer ranking signals to the new URL and update their index. Use 302 for a temporary move, where you want search engines to keep the original URL indexed. Using the wrong one can hurt your SEO during a site migration.Auth errors
401 vs 403: a common mix-up
401 Unauthorizedactually means "unauthenticated" — the server doesn't know who you are, so log in. 403 Forbiddenmeans the server knows who you are but you don't have permission. Short version: 401 is "who are you?", 403 is "you can't do that."
Common questions
What does 404 mean?
Not Found — the URL doesn't point to anything on the server. It's a client error: the request was understood, but there's no resource there. Often caused by typos, deleted pages, or broken links.
What's the difference between a 404 and a 410?
404 Not Found means the resource isn't here (and might come back). 410 Gone is stronger: the resource was intentionally removed and won't return. Search engines de-index 410s faster than 404s.
What causes a 502 or 504?
Both involve a gateway or proxy server. 502 Bad Gateway means it got an invalid response from an upstream server; 504 Gateway Timeout means the upstream server didn't respond in time. They usually point to a backend that's down, overloaded, or misconfigured.
Is 200 always good?
200 means the HTTP request succeeded, but the response body could still contain an application-level error (some APIs return 200 with an error message inside). For REST APIs, well-designed endpoints use the right status code rather than always returning 200.
What's a 429?
Too Many Requests — you've hit a rate limit. Slow down and retry later; the response often includes a Retry-After header telling you how long to wait.