HTTP Status Codes — Complete Reference

What does a 404 error mean?

A 404 error means the server could not find the page you requested. The page may have been deleted, moved to a different URL, or the link you followed may contain a typo. It is the most commonly seen error on the web.

What is the difference between a 301 and 302 redirect?

A 301 redirect is permanent and tells search engines to update their index and transfer ranking signals to the new URL. A 302 redirect is temporary and tells search engines to keep the original URL. Use 301 for permanent moves and site migrations.

What causes a 500 Internal Server Error?

A 500 error means something went wrong on the server without a specific cause identified. Common culprits include a broken PHP script, incorrect server configuration, a corrupted .htaccess file, or the server running out of memory.

What is a 403 Forbidden error?

A 403 error means the server understood your request but is refusing to provide access. This can happen due to incorrect file permissions, not being logged in to an account, or the server administrator blocking access to that specific resource.

What is the difference between a 301 and 302 redirect?

A 301 Moved Permanently redirect tells search engines and browsers that the resource has moved for good. Browsers cache it, and search engines transfer link equity to the new URL. A 302 Found redirect is temporary — search engines keep indexing the original URL and browsers do not cache it. Use 301 for permanent site migrations, 302 only when the move is genuinely temporary.

What causes a 500 Internal Server Error?

A 500 error means something went wrong on the server itself, not with your request. Common causes include a misconfigured .htaccess file, a PHP script that threw an uncaught error, a database connection failure, or running out of server memory. As a visitor, there is nothing you can do — the site owner must fix it. Check the server error logs for the specific cause.

What does a 429 Too Many Requests error mean?

A 429 response means you have exceeded the server's rate limit — you sent too many requests in a short time. The response usually includes a Retry-After header specifying when you can try again. Rate limiting protects APIs and servers from abuse and overload. If you hit a 429 in your code, implement exponential backoff: wait, then retry with increasing delays.