4xx errors

Last updated 18 June 2026 2 min

4xx HTTP status codes are a server's way of saying "your request can't be delivered" — meaning the request itself was wrong, blocked, or unauthorised. They're distinct from 5xx errors (server problems) and 3xx codes (redirects).

Common 4xx codes

400 Bad Request — the request was malformed (bad syntax, invalid characters). Often caused by corrupted cookies.
401 Unauthorised — required authentication was missing or invalid. The user needs to log in successfully.
403 Forbidden — the server understood the request but refuses to fulfil it. The user is identified but lacks permission. Common with directory access restrictions, IP blocks, or WAF rules.
404 Not Found — the requested URL doesn't exist on the server.
405 Method Not Allowed — the HTTP method (GET, POST, etc.) isn't permitted on this endpoint.
408 Request Timeout — the client took too long to send the full request.
410 Gone — like a 404, but explicitly tells the client the resource is permanently removed. Search engines drop 410s from the index faster than 404s.
429 Too Many Requests — rate limiting; the client has sent too many requests in a given time.

SEO impact

404 and 410 — both signal the page is unavailable. 410 tells Google to drop the URL more quickly, as the URL was purposefully removed; 404 leaves room for the URL to come back, and allows for the possibility that it is a temporary issue.
403 and 401 — these prevent crawling. Google treats these as access-denied and will eventually drop the URLs from search results.
429 — if Googlebot hits rate limits, crawl frequency drops. Server logs and Search Console's Crawl Stats report will flag this.
400 and 405 — usually edge cases for human users, but recurring 400s in logs often indicate a deeper system bug.

Fixing 4xx errors

Redirect or restore if the URL has a valid replacement.
Return 410 for permanently removed content you want deindexed quickly.
Update internal links so the site doesn't point to 404s for removed pages.
Check authentication and permissions for unexpected 401/403 errors on public pages.
Investigate rate limits if 429s appear in crawl logs.

Disclaimer: All information contained herein is for informational purposes only. It is not advice or instructional.