HTTP Status Codes Cheat Sheet

HTTP status codes are three-digit numbers returned by a web server in response to a client's request. They indicate whether the request was successful, redirected, or resulted in an error. Codes are grouped into five classes: 1xx (Informational), 2xx (Success), 3xx (Redirection), 4xx (Client Error), and 5xx (Server Error).

A 301 redirect is permanent, meaning the resource has permanently moved to a new URL. Search engines transfer SEO value to the new URL. A 302 redirect is temporary, indicating the resource is temporarily at a different URL. Search engines keep indexing the original URL. Use 301 for permanent URL changes and 302 for temporary redirects.

401 Unauthorized means the request lacks valid authentication credentials — the user needs to log in. 403 Forbidden means the user is authenticated but doesn't have permission to access the resource. In short: 401 = "Who are you?" and 403 = "I know who you are, but you can't access this."

Use 404 Not Found when a resource doesn't exist or may have never existed. Use 410 Gone when a resource has been intentionally and permanently removed. The key difference is that 410 tells search engines to remove the page from their index faster, while 404 may be recrawled periodically. Use 410 when you deliberately delete content.

A 500 Internal Server Error is a generic catch-all error indicating something went wrong on the server side. The server encountered an unexpected condition that prevented it from fulfilling the request. Common causes include unhandled exceptions in code, misconfigured servers, database connection failures, or syntax errors in server-side scripts. Check server logs for specific details.