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HTTP Status Codes Reference

Searchable reference for the 50 HTTP status codes developers meet in practice, with RFC 9110 names and plain-English descriptions. Filter by class, one-click copy.

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The first digit tells you almost everything

Every HTTP response carries a three-digit status code, and the first digit tells you almost everything. RFC 9110, the 2022 specification that consolidated the older HTTP standards, defines five classes: 1xx is informational, 2xx is success, 3xx is redirection, 4xx is a client error, and 5xx is a server error. A client that understands nothing else can still act correctly by branching on that first digit — a 2xx means proceed, a 4xx means fix the request, a 5xx means retry later. The specific number then narrows the meaning. This reference lists the 50 codes you actually meet in browsers, server logs, and API responses, searchable by number, name, or keyword.

The 1xx and 2xx classes cover the smooth path. 100 Continue lets a client check, before sending a large body, that the server will accept it; 101 Switching Protocols is the handshake that upgrades an HTTP connection to a WebSocket. In the 2xx range, 200 OK is the default success, 201 Created follows a POST that made a new resource and should carry a Location header pointing to it, 204 No Content answers a successful DELETE with an empty body, and 206 Partial Content returns a byte range, which is what makes resumable downloads and video seeking work.

3xx: the redirects people mix up

The redirection class is where the subtle distinctions live, and getting them wrong changes behavior. 301 Moved Permanently and 308 Permanent Redirect both say the resource has a new home, but 301 historically let clients rewrite a POST into a GET, while 308 forbids changing the method — the body and verb survive the hop. The same split runs through the temporary pair: 302 Found may change the method, 307 Temporary Redirect must not. 303 See Other is the one people forget, and it is the backbone of the POST/Redirect/GET pattern: after a form submission the server answers 303, and the browser fetches the result page with a fresh GET, so a refresh does not resubmit the form. And 304 Not Modified carries no body at all — the server confirming a cached copy is still valid in response to a conditional request.

4xx: the client-error pairs that confuse

The 4xx class blames the client, and two pairs cause the most confusion. 401 Unauthorized actually means unauthenticated: the request lacked valid credentials, and sending them may fix it. 403 Forbidden means the server knows who you are and still refuses — more credentials will not help. The second pair separates syntax from meaning: 400 Bad Request is for a malformed request the server cannot parse, while 422 Unprocessable Content is for a request that parsed fine but is semantically wrong, such as valid JSON with an invalid field value. Rate limiting has its own code, 429 Too Many Requests, usually sent with a Retry-After header; 410 Gone is a stronger 404 for a resource deliberately removed for good; and 451 Unavailable For Legal Reasons — named after Fahrenheit 451 — marks content blocked by law rather than by a technical fault.

5xx: the server admitting fault, and where it happened

The 5xx class is the server admitting fault, and the gateway codes localize the failure. 500 Internal Server Error is the generic catch-all for an unexpected condition with nothing more specific to say. 502 Bad Gateway and 504 Gateway Timeout both come from a proxy or load balancer standing in front of the real server: 502 means the upstream returned something invalid, while 504 means the upstream did not answer in time. 503 Service Unavailable signals a temporary overload or maintenance window and, like 429, may carry Retry-After to tell clients when to come back. Distinguishing these matters operationally, because a 502 points at the application while a 504 points at latency or a dead upstream.

Two practical notes

First, the single most common API anti-pattern is returning 200 OK with an error message in the body: it defeats caching, breaks automatic retry logic, and hides failures from monitoring that watches status codes rather than payloads — the code should reflect the outcome. Second, this list is a curated reference of the roughly 50 standardized codes developers meet in practice, not the full IANA registry, and it does not include vendor-specific numbers like nginx 499 or the Cloudflare 520 through 524 range that appear only in specific stacks. Everything here runs in your browser as a static lookup, with no request sent anywhere when you search.

How to Use

1

Search by code number, name, or keyword.

2

Filter by class: 1xx, 2xx, 3xx, 4xx, 5xx.

3

Click any code to copy it.

Features

50 codes across all five classes with RFC 9110 names
Search by code, name, or description
Filter by class: Informational, Success, Redirection, Client Error, Server Error
Color-coded by class for fast scanning
One-click copy for any code

Common Questions

About HTTP Status Codes

Look up the 50 HTTP status codes you actually meet in browsers, logs, and APIs — from 100 Continue to 511 — with RFC 9110 names and plain-English descriptions. Search by code, name, or keyword, filter by class (1xx Informational, 2xx Success, 3xx Redirection, 4xx Client Error, 5xx Server Error), and copy any code with one click. Explains the tricky pairs like 401 vs 403 and 301/302/303/307/308.

Also known as: http codes, status code meaning, 404 500 codes, http response codes, http error codes, 301 vs 302, 401 vs 403, 400 vs 422, what is 503, rfc 9110 codes, http status list, server error codes, redirect status codes, rest api status codes.

Processing Note

HTTP Status Codes runs in your browser, so the input you enter is processed locally on this page and is not uploaded to a ToolMintX account.

Tool Limits

IT tools provide quick diagnostics and transformations. They cannot see every private network, deployment setting, proxy, firewall, or production edge case.

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