HTTP status codes
Type a code like 404 or a word like redirect or timeout and get a plain explanation, the usual causes, how to fix it and what it means for search engines. Each code has its own link, for example #503, so you can share the exact answer. Includes nginx's 499 and Cloudflare's 520 to 526.
48 status codes
How it works
- •Search by code (typing 40 shows every 40x), by name or by any word. The tabs filter by group: information, success, redirection, client error and server error.
- •Open a code to see what it means, common causes, how to fix it and the SEO impact. The link changes to #404 and so on; use the button to copy a link to that code.
- •The first digit tells you who is at fault: 4xx means the request was wrong or refused, 5xx means the server failed.
What it does and what it cannot do
- •It is a reference, not a diagnosis. Your server log tells you which cause applies.
- •SEO notes describe how search engines usually behave; they do not publish exact thresholds.
- •Non-standard codes (nginx 499, Cloudflare 520 to 526) are marked with their vendor; they are not part of the HTTP standard.
- •Codes that almost never appear on the open web (for example 102, 226 or 506) are left out.
Questions
- What is the difference between 301 and 302?
- 301 means the page moved for good and search engines should move its ranking to the new address. 302 means a temporary move, so the old address stays indexed.
- What is the difference between 404 and 410?
- 404 says nothing exists here now, possibly only for a while. 410 says it was removed on purpose and will not return, and search engines tend to drop it from the index slightly sooner.
- What is a soft 404?
- A page that shows 'not found' but answers with status 200. Search engines treat it as an error and report it in Search Console. Return a real 404 or 410.
- How do I fix a 502 or 504 error?
- Both mean a gateway or proxy did not get a good answer from the server behind it. Check that the backend is running, read both logs, and look for slow requests or timeouts that are too short.
- Which codes hurt SEO most?
- Long-lasting 5xx errors (crawling slows and pages drop out), 404s on pages that have backlinks, redirect chains and loops, and soft 404s. A 503 with Retry-After is the right way to announce short maintenance.