A complete guide to the HTTP Status Code Reference tool, the five status code categories, and commonly misunderstood codes worth knowing.
Launch the HTTP Status Code Reference →The HTTP Status Code Reference is a searchable, filterable lookup tool covering 62 official HTTP status codes, each shown with its official name, category (Informational, Success, Redirection, Client Error, or Server Error), and a plain-language explanation of what it means and when a server typically returns it. You can search by the numeric code itself, by name, or by keyword, and filter results down to a specific category using the chip-style filter buttons above the results list.
This is a pure reference tool with no network dependency: every piece of data shown is static content, drawn from the official IANA (Internet Assigned Numbers Authority) HTTP Status Code Registry and the current HTTP semantics specification, RFC 9110.
HTTP status codes are one of those things that almost everyone working with websites, APIs, or web development encounters constantly, but rarely remembers in full detail beyond the handful of codes seen most often (200, 404, 500). When something less common shows up — a 429 Too Many Requests while testing an API, a 451 Unavailable For Legal Reasons on a geo-restricted resource, or a 507 Insufficient Storage from a WebDAV server — having a fast, authoritative, searchable reference beats trying to remember or guess at the meaning, and beats searching a general search engine and sorting through results of varying quality and accuracy.
Centralizing this information from its authoritative sources, rather than relying on secondhand paraphrasing found scattered across the internet, means the explanations here are grounded directly in how the codes are officially defined, including codes that are less commonly discussed but still show up in real-world situations, like 103 Early Hints or 425 Too Early.
HTTP status codes are grouped into five categories based on the first digit of the three-digit code, and understanding this grouping alone is often enough to get useful information even before looking up the exact specific code:
Knowing just the category of an unfamiliar code — is this a 4xx or a 5xx — immediately tells you whether to look at the request being made (client-side) or the server receiving it (server-side), which is often the single most useful first step in diagnosing an unexpected status code.
404, a keyword like timeout, or a partial name like redirect.Searching for 418 reveals that it is officially named "I'm a teapot," an April Fools' joke originally defined in RFC 2324 as part of the Hyper Text Coffee Pot Control Protocol, which some servers have adopted in earnest to humorously deny automated or bot-like requests — a genuinely real, if unusual, part of the official status code registry.
A handful of status codes are frequently misused or misunderstood in ways that matter for anyone building or debugging web applications:
Retry-After header the server may include indicating how long to wait before trying again.Recognizing the distinction between codes that sound similar but mean genuinely different things, like 401 versus 403, or 400 versus 422, is often the fastest path to correctly diagnosing why a request is failing, rather than treating any 4xx code as an undifferentiated generic client error.
The specific codes, names, and categories presented in this tool are sourced from two authoritative references: the IANA HTTP Status Code Registry, which is the official, continuously maintained registry of all assigned HTTP status codes, and RFC 9110 (HTTP Semantics), the current Internet Engineering Task Force specification that formally defines HTTP's core semantics, including the meaning of each status code category and most individual codes.
Because this reference is static content baked directly into the page rather than fetched from a live external source, there's no possibility of the data being temporarily unavailable or slow to load due to a third-party service outage, though it also means the list reflects the registry as it stood at the time this tool was built, rather than updating automatically if new codes are ever formally registered in the future.
This tool makes no network requests of any kind. All status code data is included directly in the page itself and all searching and filtering happens through plain JavaScript running in your browser. Nothing you search for is transmitted anywhere, logged, or stored.
This reference focuses on the 62 codes formally registered in the IANA registry as standard, documented status codes. Some additional codes exist as non-standard extensions used by specific products or platforms (certain CDNs and cloud providers define their own supplementary codes), which fall outside the scope of the official registry this tool is built from.
401 Unauthorized technically means the client needs to authenticate itself before the request can be processed (despite the confusing name, it's really about missing or invalid authentication). 403 Forbidden means the server understood exactly who is making the request and has deliberately decided to deny access regardless of authentication status.
Yes, in a limited but genuine way. Some services and APIs use it intentionally and humorously as a way to signal that a request has been deliberately refused, often for anti-automation purposes, leaning into its origin as an April Fools' joke rather than treating it purely as a historical curiosity.
The search matches against the code number, the official name, and the full explanation text, so a keyword that appears anywhere in a code's description will surface that result, even if it isn't part of the code's formal name.