The HTTP Status Codes tool is a browser-based reference for the 64 individual HTTP response codes registered by the Internet Assigned Numbers Authority (IANA), each one captured from the official HTTP Status Code Registry as of July 17, 2026. It is designed as a focused, registry-only alternative to general web documentation: instead of serving a long, mixed list of vendor-specific extensions, undocumented three-digit values, and informal nicknames, it shows only the codes that IANA has actually assigned, with their official reason phrase, a concise meaning, a registration-state label, and a direct RFC reference. Search supports exact codes, full-class patterns, partial phrases, and RFC numbers, and the matching happens locally in your browser. Each row links to the governing specification so implementation-critical details can be checked against the original text. This combination of a narrow boundary, a dated snapshot, and authoritative citations makes the HTTP Status Codes tool a precise answer to a specific question: what does the standards body say this code is, and what rule governs it.
Why You Might Want a Registry-Only HTTP Status Codes Alternative
General web documentation tends to mix three different things into one list: codes that IANA has formally registered, codes that individual frameworks emit without any registry assignment, and informal nicknames that have drifted away from the current specification. When you need a fast answer to a specific question such as whether this code is current, what it means, and which RFC governs it, that mash-up is slow to navigate and easy to misread. The HTTP Status Codes tool takes a deliberately different approach: it is a registry-only reference for the 64 individual entries that IANA has captured, and nothing else.
That boundary is the main reason to use it as an alternative. Vendor-specific extensions such as a framework's own error code are not present, because the IANA registry does not describe them. Unassigned ranges are not present either, so a search for a number such as 105 returns a clear empty result with an explanation rather than a guess. The familiar nickname associated with 418 does not appear as the current description, because the snapshot of the registry and RFC 9110 label 418 as unused. Each of those choices reduces the chance of acting on a phrase that the standards have already retired.
The Five Response Classes at a Glance
HTTP response codes are grouped into five classes by their first digit. The class is broader than any single code: 404 Not Found and 429 Too Many Requests are both client-error responses, but they point to different conditions and usually call for different remedies. The table below is the shared starting point that any registry entry sits inside.
| Class | Range | General meaning | Example |
|---|---|---|---|
| 1xx Informational | 100-199 | Interim progress; the request was received and is being processed. | 100 Continue |
| 2xx Successful | 200-299 | The request was understood, accepted, and handled. | 200 OK |
| 3xx Redirection | 300-399 | Further action is required to complete the request, typically a redirect. | 301 Moved Permanently |
| 4xx Client error | 400-499 | The request could not be fulfilled because of a client-side condition. | 404 Not Found |
| 5xx Server error | 500-599 | The server failed to fulfill an apparently valid request. | 500 Internal Server Error |
Knowing the class narrows a search before you even start typing. If you already know the request reached the server and the server replied that something was wrong, you can limit the table to the 5xx range; if you suspect the request itself was malformed, start in 4xx.
How to Look Up a Code
The reference has two controls: a search box that accepts several different kinds of input, and a response-class selector that limits matches to one of the five classes. The steps below are the same whether you are starting from a code you saw in a log, a phrase you remember, or an RFC number.
- Enter an exact three-digit code such as 404, a class pattern such as 4xx, a reason phrase such as Not Found, a concept such as gateway, or a protocol term such as WebDAV in the search box.
- Choose Informational, Successful, Redirection, Client error, or Server error from the response-class selector when you want to narrow the table to a single class.
- Read the phrase, concise meaning, registration-state label, and RFC reference for each row that matches.
- Click the linked RFC for implementation-critical details such as method-specific semantics, caching rules, or authentication context.
Exact numeric search is strict. Entering 404 returns the 404 row only, not every description that mentions the digits four, zero, and four. Entering 4xx returns every individually registered entry in the client-error class; it does not fabricate rows for unassigned numbers. Text search checks the reason phrase, the class, the concise meaning, the RFC reference, and the registration state, so a single query like gateway pulls together 502 Bad Gateway and 504 Gateway Timeout without you needing to know both codes in advance. The class selector combines with the text query, so searching gateway while selecting Server error returns the gateway-related server failures, while searching Not Found under Server error produces a clear empty result instead of leaving a stale table visible.
Reading the State Label and Following the RFC
Registration state is information that a plain list of codes tends to drop. The tool labels each entry with the state that IANA's snapshot records for it, which means the table distinguishes between codes that are current, codes that are a temporary registration tied to an active Internet-Draft, codes that have been deprecated, codes that are unused, and codes that are obsolete. A few concrete examples are worth keeping in mind:
- 104 Upload Resumption Supported is labeled Temporary, because the registry ties it to an active Internet-Draft; temporary registrations can change or expire, so the snapshot date is part of the meaning.
- 305 Use Proxy is labeled Deprecated through RFC 9110; a row is still present, but the label warns against choosing it as an ordinary current response.
- 306 and 418 are labeled Unused; the registry and RFC 9110 reserve those numbers, even when an older, more colorful phrase is widely remembered.
- 510 Not Extended is labeled Obsolete, and is shown for completeness even though no current implementation should rely on it.
The short meaning printed beside each code is a practical paraphrase, not a replacement for the specification. Several codes have method-dependent or context-dependent semantics that the paraphrase cannot fully capture. 200 OK has method-dependent meaning; 204 No Content prohibits a response body; 304 Not Modified participates in conditional caching; 401 Unauthorized concerns missing or invalid authentication credentials despite its historical reason phrase. For any of those cases, the RFC reference is the answer, not the side panel.
What the Reference Can and Cannot Tell You
The tool explains registered protocol meanings. It does not contact a URL, inspect a server, or claim to identify an operational fault, and it does not collect or upload the text you type. Filtering happens immediately in your browser, so the search text never leaves the device. That scope is useful to know before you draw a conclusion from a code you saw in production.
Status codes communicate protocol outcomes; they do not prove the underlying cause. 502 Bad Gateway can reflect an upstream crash, a network path problem, a proxy timeout policy, or malformed upstream output; the code alone does not pick among those. 429 marks a rate limit, but the right retry behavior depends on the service and may be guided by a Retry-After header. 404 can conceal a resource that is actually forbidden, and 500 is intentionally generic. Diagnosing a live incident still requires server logs, request identifiers, response headers, and the relevant service documentation. The table tells you what the standards say a code means; the logs and headers tell you why your specific request triggered it.
If your work also takes you into JSON payloads from the same response, you can inspect them in a JSON Formatter without leaving the browser. For a closely related entry path into the same registry, see an HTTP response codes list searched by code, class, or phrase.