A status code is the first thing your code, your browser or your monitoring tool sees back from a request, and it is meant to tell you in three digits whether the request worked, whether you need to do something differently, or whether the server is the one at fault. In practice the difference between a 401 and a 403, or between a 502 and a 503, changes exactly what you should fix next, and looking that up mid debugging session should not require digging through a long specification document.
Everything runs locally in your browser. The table of codes and descriptions is bundled with the page itself, so searching it involves no network request, no rate limit and no account, which matters when you are checking a code in the middle of an outage and every second of load time counts.
The five classes an HTTP status code lookup groups codes into
Every valid status code falls into one of five classes based on its first digit, and that first digit alone tells you the general shape of what happened before you read a single word of description. 1xx codes are informational and rare in normal application code. 2xx codes mean the request succeeded. 3xx codes mean further action is needed, almost always a redirect. 4xx codes mean the client sent something the server would not accept. 5xx codes mean the server failed to handle a request that may have been perfectly valid.
Recognising the class first is often enough to triage an incident before you even open this http status code lookup. A wall of 5xx codes in your logs points at your own infrastructure. A sudden run of 4xx codes usually points at a client bug, a changed API contract, or an expired credential rather than anything wrong with the server itself.
- 1xx: informational, the request was received and processing continues.
- 2xx: success, the request was received, understood and accepted.
- 3xx: redirection, further action is needed to complete the request.
- 4xx: client error, the request contains bad syntax or cannot be fulfilled.
- 5xx: server error, the server failed to fulfil an apparently valid request.
Codes that get confused with each other
401 and 403 both mean access is denied, but for different reasons. A 401 Unauthorized means the request has no valid credentials at all, or the ones supplied were rejected, and the correct response is to authenticate. A 403 Forbidden means the server understood exactly who you are and has decided you still are not allowed to do this, and no amount of re authenticating with the same account will change that.
502, 503 and 504 are all reported as generic server errors by people who have not looked them up, but they describe different failures along a request path. A 502 Bad Gateway means a server acting as a proxy got an invalid response from an upstream server. A 503 Service Unavailable means the server is temporarily unable to handle the request, often due to overload or maintenance. A 504 Gateway Timeout means the upstream server simply never responded in time. Distinguishing between the three usually points straight at which layer of a system is actually failing.
301 and 302 look similar in a browser, both silently following the redirect, but they mean different things to a search engine and a caching layer. 301 Moved Permanently tells a crawler to transfer ranking signals to the new URL and update its records. 302 Found means the move is temporary and the original URL should stay indexed. Using 302 for a permanent move, or 301 for a temporary one, is a common cause of ranking problems that only surface weeks later.
Reading an api error code reference during debugging
Most APIs layer their own error semantics on top of the standard status codes, using the response body to add detail a bare three digit number cannot carry. A well designed api error code reference in an API's own documentation will tell you exactly which fields to expect in a 400 or 422 response body, but the status code itself is still the fastest first signal, because it tells you the category of problem before you have parsed a single byte of JSON.
422 Unprocessable Entity is worth calling out specifically because it is frequently confused with 400 Bad Request. A 400 usually means the request itself is malformed, invalid JSON or a missing required header. A 422 means the request was syntactically fine and was understood, but the values inside it fail some validation rule, such as an email address that is not actually shaped like an email address.
Why the http status codes list still matters with modern tooling
Modern frameworks often hide the status code behind a helper method, a try catch block or an automatically thrown exception, which makes it easy to go months without directly seeing the number your server actually sent. That convenience disappears the moment something behaves unexpectedly in production, at which point you are reading raw response codes in a load balancer log or a browser network panel with no framework standing between you and the number.
Keeping the full http status codes list in your head is unnecessary. Keeping the meaning of the fifteen or so codes you see regularly is genuinely useful, and this lookup exists for the long tail: the 451 you have never seen before, the 425 a new client library just started sending, or the exact wording of a code you half remember but do not want to guess at while writing an incident report.
Searching what does status code mean without leaving your workflow
Typing a bare number into a general search engine to answer what does status code mean works, but it routes you through a results page, an ad, and often a site that reformats the same paragraph from the specification with extra padding around it. This tool skips all of that: type the number, get the row, keep working. An http response code search here returns the same row whether you searched by digit or by word, since both paths filter the identical underlying table.
Searching by keyword works the same way as searching by number. Typing cache, auth, or redirect filters the table down to every status code whose name or description matches, which is a faster way to browse a category of codes than scanning a long list top to bottom looking for the ones that are relevant to the bug you are actually chasing.
| Code | Name | Class | Typical cause |
|---|---|---|---|
| 200 | OK | Success | The request succeeded and the body contains the result |
| 301 | Moved Permanently | Redirection | The resource has a new permanent URL |
| 400 | Bad Request | Client error | The request syntax or parameters are invalid |
| 401 | Unauthorized | Client error | No valid credentials were supplied |
| 403 | Forbidden | Client error | The credentials are valid but access is denied |
| 404 | Not Found | Client error | No resource exists at the requested URL |
| 429 | Too Many Requests | Client error | The client has exceeded a rate limit |
| 500 | Internal Server Error | Server error | An unhandled fault occurred on the server |
| 503 | Service Unavailable | Server error | The server is temporarily overloaded or down for maintenance |
How to use the HTTP status code lookup
- 1
Open the search box
The table of every standard status code is already loaded and visible above the search box.
- 2
Type a number or a keyword
Enter a code like 404, or a word like timeout or redirect, and the table filters as you type.
- 3
Read the class and description
Each row shows the code, its short name, its class such as client error or server error, and a plain description.
- 4
Check the related codes
For commonly confused codes, compare the description against its neighbours before deciding which one applies to your case.
Related tools worth bookmarking
Sources and further reading
- RFC 9110: HTTP SemanticsThe current standard defining every status code class and the meaning of each registered code.rfc-editor.org
- MDN: HTTP response status codesBrowser focused reference documentation for each status code, including usage notes for web developers.developer.mozilla.org
- Google Search Central: HTTP and network errorsExplains how Google's crawler interprets redirect and error status codes for indexing purposes.developers.google.com
Frequently asked questions
Common questions about the http status code lookup.
A 401 Unauthorized means no valid credentials were supplied, or the ones given were rejected, so authenticating again can fix it. A 403 Forbidden means the server knows exactly who you are and has decided the action is not allowed regardless, so re authenticating with the same account changes nothing.
Use 301 Moved Permanently when a URL has moved for good and you want search engines to transfer ranking signals to the new address. Use 302 Found for a temporary move where the original URL should stay indexed and keep receiving traffic once the temporary situation ends.
429 Too Many Requests means you have sent more requests than the server's rate limit allows in the current time window. The response often includes a Retry-After header telling you how long to wait before trying again, which is worth checking before simply retrying immediately.
No. Every code, name and description is bundled into the page as a plain JavaScript array, and typing in the search box filters that array in memory. That local filtering is also why a result appears the instant you type a digit, with no round trip to wait for.
Some load balancers, proxies and libraries define extra codes outside the official range to represent situations the standard set does not cover, such as a client side network timeout. These are not part of the formal specification, so their meaning depends entirely on the specific tool that produced them.
502 Bad Gateway means a proxy received an invalid response from an upstream server. 503 Service Unavailable means the server itself is temporarily unable to handle requests, often due to overload. 504 Gateway Timeout means an upstream server never responded within the time allowed, which usually points at a slow dependency rather than a crash.