A 404 (Not Found) tells browsers and crawlers that nothing lives at the URL. It is the correct response for pages that never existed or were removed without a replacement.
404s become a problem when your own site links to them or when valuable URLs with external links start returning them.
Internal links to 404 pages waste crawl budget and frustrate visitors. Removed pages with backlinks lose their link equity unless they are redirected.
VisibilityKit Crawler finds every URL returning a 404 and shows which pages link to it, so you can update the links or add redirects, then verify the fix with a fresh check.
404s on URLs nobody links to are normal. Internal links to 404s and 404s on pages with backlinks are worth fixing.
404 means not found. 410 means gone on purpose. Search engines may drop a 410 slightly faster.
A link whose destination returns an error, usually a 404 or a server error, instead of a working page.
Three-digit codes a server returns with every response to say whether the request succeeded, redirected or failed.
A page that looks like an error or empty page to users but returns a 200 OK status to crawlers.
A 301 redirect signals a permanent move; a 302 signals a temporary one.
A list pairing old URLs with the new URLs they should redirect to, used during site migrations.
A desktop SEO crawler for macOS, Windows and Linux. Find what is broken, assign the work, then verify every fix. Crawl data stays on your machine.
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