HTTP Status Codes
A quick reference of 60 common HTTP status codes with meanings and category filters — stop digging through docs when debugging APIs.
| CODE | PHRASE | Meaning |
|---|
>_ USAGE GUIDE
A quick reference of 60 common HTTP status codes: each entry lists the code, its canonical name, a plain-language explanation, and what to check next. Filter by category — 2xx success, 3xx redirection, 4xx client errors, 5xx server errors — and find the meaning of 401, 403, 429, or 502 without digging through the RFC.
- Look up your code: search or scroll to the status your API returned
- Filter by class: narrow the table to redirects, client errors, or server errors
- Follow the guidance: each row gives the meaning and the usual debugging direction
The table suits two audiences: developers who want a desk manual for debugging API errors, and newcomers learning what HTTP responses actually mean. Every entry was chosen from real-world traffic, so the codes you actually encounter — 400, 401, 404, 429, 500, 502, 504 — are the ones documented in depth. It is a purely static reference — rendered locally in your browser, no network requests, fully usable offline, and completely free.
>_ FAQ
Q1 · What does HTTP 404 mean?
Not Found — the server cannot find the requested resource: the URL is misspelled, the resource was deleted, or the route is not configured. Do not confuse it with 410 (Gone), which explicitly states the resource is permanently removed. When debugging a 404, check the request path and proxy configuration first rather than assuming the server is down.
Q2 · What is the difference between 401 and 403?
401 Unauthorized means unauthenticated — the server does not know who you are: not logged in, or the token is missing or expired. 403 Forbidden means authenticated but not allowed — the server knows who you are and you lack permission. The debugging directions differ completely: for 401, check the login state and token passing; for 403, check permission and role configuration. Repeatedly re-logging-in after a 403 is a classic wrong turn.
Q3 · What is the difference between 502 and 504?
Both come from a reverse proxy or gateway in front of your app. 502 Bad Gateway means the backend crashed or returned an invalid response — check the application process and port. 504 Gateway Timeout means the backend is alive but too slow — look for slow queries, deadlocks, or a stuck external dependency. Same location, two different root causes, two different checklists.
Q4 · What is the difference between 301 and 302 redirects?
301 is permanent: browsers and search engines cache the new address and SEO weight transfers to it — use it for domain moves and URL restructuring. 302 is temporary: nothing is cached and no weight transfers — use it for campaign jumps and post-login redirects. Mixing them up has real consequences: a temporary redirect that should have been 301 gets cached by browsers, and correcting it later is painful.
Q5 · What is HTTP 418?
418 "I'm a teapot" began as an April Fools' joke in 1998 and is occasionally used in production as an anti-scraping easter egg. Related oddities include 425 (Too Early) and 451 (Unavailable For Legal Reasons). The reference table includes these for reading other people's code — for your own production systems, stick to standard codes so gateways and clients interpret them correctly.