HTTP Status Codes Reference - Complete Guide with Search & Categories

What is the difference between 4xx and 5xx status codes?

4xx status codes indicate client errors — the request contains invalid syntax, unauthorized access, or cannot be fulfilled due to a client-side issue. For example, 404 Not Found means the resource does not exist. 5xx status codes indicate server errors — the server failed to fulfill a valid request due to an internal issue, such as 500 Internal Server Error or 503 Service Unavailable. The key difference is whether the problem is with the client's request or the server's ability to process it.

What is the most common HTTP status code?

200 OK is the most common HTTP status code for successful requests. For errors, 404 Not Found is the most well-known code. In modern web applications, 301/302 redirect status codes are also extremely common for URL redirection. On the server side, 500 Internal Server Error is the most generic and common server error code. According to web traffic analysis, approximately 70-80% of requests return 2xx codes, 5-10% return 3xx redirects, 5-15% return 4xx client errors, and 1-5% return 5xx server errors.

Can HTTP status codes be customized?

While the standard HTTP status codes are defined by the IANA and RFC specifications, custom status codes can be used in some contexts. However, doing so is not recommended because clients, proxies, and browsers may not understand custom codes. The standard codes cover virtually all common scenarios. Some applications use non-standard codes internally, but they should always map to standard codes when communicating with external clients. The HTTP specification reserves the status code ranges for specific categories (1xx-5xx) and recommends using the most appropriate existing code rather than creating custom ones.

What is the 418 I'm a Teapot status code?

The 418 I'm a Teapot status code is an April Fools' Day joke defined in RFC 2324 (Hyper Text Coffee Pot Control Protocol) published on April 1, 1998. It means the server refuses to brew coffee because it is a teapot. While it is an officially registered HTTP status code, it is not intended for real-world use. Some developers and frameworks include it as an Easter egg or for testing purposes. It has become one of the most well-known humorous elements in the HTTP specification.

How should I handle 301 vs 302 redirects?

Use 301 Moved Permanently when a resource has been permanently moved to a new URL. Search engines will update their index to the new URL and stop crawling the old one. Use 302 Found (or 307 Temporary Redirect) when the redirect is temporary, such as during maintenance or A/B testing. Search engines will continue to index the original URL. For modern applications, consider using 308 Permanent Redirect (preserves request method) and 307 Temporary Redirect (preserves request method) as more explicit alternatives to 301 and 302.