Every time a browser or crawler asks a server for a resource, the server replies with a three-digit status code. That code tells the client whether the request succeeded, was redirected, failed because of bad input, or failed because of a server problem. Understanding these codes is essential for developers, SEOs, and site operators.
This HTTP status codes reference groups every common response into five categories and lets you search or filter by class. Whether you are debugging an API, fixing crawl errors, or setting up redirects, the explanation you need is a click away.
All filtering happens in the browser, so the tool responds immediately even if you are working offline after the first load.
Codes are grouped by their first digit:
Search engines treat status codes as signals about the health of your site. A 200 OK means the page can be indexed. A 301 Moved Permanently passes most ranking signals to the new URL. A 302 Found is treated as temporary and does not pass full equity. 404 Not Found removes a URL from the index over time, while 500 Internal Server Error tells crawlers your site is unreliable and may reduce crawl frequency.
200 OK is the standard success response. 301 Moved Permanently and 308 Permanent Redirect are used when a page has a new permanent home. 400 Bad Request means the server could not understand the request, often due to malformed syntax. 401 Unauthorized and 403 Forbidden both deny access, but 401 implies authentication is possible while 403 rejects access outright. 404 Not Found means the resource does not exist at that URL. 500 Internal Server Error, 502 Bad Gateway, 503 Service Unavailable, and 504 Gateway Timeout all point to server-side problems.
When a page breaks, start by checking the status code in your browser's network tab or with a tool like this reference. A 4xx error tells you to fix the request or link. A 5xx error tells you to check server logs, load balancers, or upstream services. Pair this workflow with the Regex Tester for parsing logs and the UUID Generator when you need unique request identifiers.
Type in the search box to find specific status codes by number or name
Click category buttons to filter by 1xx, 2xx, 3xx, 4xx, or 5xx
Click on any status card to see detailed description and use cases
HTTP status codes are essential for understanding web communications. Our comprehensive reference helps developers quickly look up any status code and understand what it means for their applications.
1xx Informational: The request was received, continuing processing.
2xx Success: The request was successfully received, understood, and accepted.
3xx Redirection: Further action must be taken to complete the request.
4xx Client Error: The request contains bad syntax or cannot be fulfilled.
5xx Server Error: The server failed to fulfill a valid request.
An HTTP status code is a three-digit response sent by a server to indicate the result of a request. Codes are grouped into five classes: 1xx informational, 2xx success, 3xx redirection, 4xx client error, and 5xx server error.
200 OK means the request succeeded and the server returned the requested resource. It is the normal response for a working page.
301 is a permanent redirect that passes most ranking signals to the new URL. 302 is a temporary redirect and should be used when the original URL will return later.
404 means the server cannot find the requested resource at the given URL. Search engines will eventually drop 404 pages from their indexes.
500 indicates an unexpected server-side problem. It usually requires checking application logs, database connections, or server configuration.
503 means the server is temporarily unable to handle the request, often due to maintenance or overload. It is the correct code to use during planned downtime.
Yes. Search engines use status codes to decide whether to index a page, follow a redirect, or reduce crawl frequency. Persistent 5xx errors can hurt rankings.
Use the category buttons to show only 1xx, 2xx, 3xx, 4xx, or 5xx codes, or type a number or keyword into the search box.
400 means the server could not understand the request, usually because of malformed syntax, invalid parameters, or encoding issues.
403 means the server understood the request but refuses to authorize it. Unlike 401, authentication will not grant access.
Yes, it is completely free with no signup and no usage limits.
The reference covers the most common standardized codes from 100 to 599, including the ones most relevant to web developers and SEOs.
