HTTP Status Code Lookup
Look up any HTTP status code with plain-English explanations.
1xx — Informational
2xx — Success
3xx — Redirection
4xx — Client Error
5xx — Server Error
What Are HTTP Status Codes?
HTTP status codes are three-digit numbers returned by web servers to indicate the result of a client's request. They were standardized in the HTTP/1.0 specification (RFC 1945) and expanded in HTTP/1.1 (RFC 7231). Every time your browser loads a page, downloads a file, or submits a form, the server responds with a status code that tells the client whether the request succeeded, failed, or requires further action.
The Five Categories
Status codes are grouped into five categories. 1xx (Informational) — the request was received, processing continues. 2xx (Success) — the request was successfully received and processed. 3xx (Redirection) — further action is needed to complete the request. 4xx (Client Error) — the request contains an error on the client side. 5xx (Server Error) — the server failed to fulfill a valid request. Understanding these categories helps you quickly diagnose issues.
Most Important Codes for SEO
200 (OK) is the only code that means your page is working correctly. 301 (Moved Permanently) preserves SEO value when moving content. 302 (Temporary Redirect) doesn't pass full ranking signals. 404 (Not Found) means lost content — set up redirects for important deleted pages. 410 (Gone) tells Google to de-index a page faster than 404. 500 and 503 errors can cause Google to temporarily or permanently drop pages from its index.
301 vs 302 Redirects
This is one of the most critical distinctions in SEO. A 301 redirect tells search engines the move is permanent — ranking signals and link equity transfer to the new URL. A 302 indicates a temporary move — search engines keep indexing the original URL. Using a 302 when you mean 301 can split your SEO value and confuse search engines. Always use 301 for permanent URL changes.
How to Check Status Codes
You can check status codes using browser DevTools (Network tab), command-line tools (curl -I URL), or online tools like httpstatus.io. Google Search Console reports crawl errors including 404s and server errors. Tools like Screaming Frog can audit your entire site for status code issues. Regular monitoring helps catch problems before they impact SEO or user experience.