HTTP Status Codes (for SEO)
HTTP status codes are the three-digit responses a server returns for every request. Google reads them as indexing instructions: 2xx pages can be indexed, 3xx transfer signals to the target, 404/410 drop URLs, and 5xx slows crawling.
The status code is the first thing Googlebot evaluates on every fetch — before content, meta tags, or structured data — and each class maps to a distinct indexing outcome. A 2xx response hands content to indexing. A 3xx response is followed as a 301 or 302 redirect and read as a canonicalization signal. A 4xx response removes the URL from the index. A 5xx or 429 response tells Google to back off.
One code is pure efficiency: 304 Not Modified. Googlebot sends conditional requests (If-Modified-Since, ETag) for URLs it has already indexed; answering 304 confirms the stored copy is still current, skips the download, and saves crawl budget for URLs that changed.
Status codes are also the failure modes. Persistent 5xx responses drop pages from the index, and a robots.txt file that itself returns 5xx makes Google temporarily treat the entire site as disallowed — the fastest way a single misconfigured file stops site-wide crawling. Check what any URL really returns with the HTTP Header Checker.
Quick facts
Which status codes can Google index?
Only 2xx responses — in practice 200 — deliver content Google considers for indexing. A 200 is a precondition, not a guarantee: the page still passes quality evaluation, and the ones that fail land in Crawled – currently not indexed.
Two 200-adjacent cases matter. A soft 404 — a 200 whose content is an error or empty page — gets reclassified as a 404 and excluded, which is why deleted content needs a real 404 or 410 rather than a friendly "not found" page returning 200. And a 304 Not Modified answer to a conditional request keeps the existing indexed copy: nothing is re-downloaded, no signals are lost, and the saved fetch goes to a URL that changed.
What is the difference between 404 and 410 for Google?
Both drop the URL from Google's index. A 410 (Gone) does it marginally faster because it declares the removal deliberate; a 404 (Not Found) is ambiguous — the content is absent, but the server does not say why — so Googlebot rechecks 404s before treating them as final.
404s carry no site-wide penalty: URLs disappearing is normal web behavior, and Google evaluates the pages that exist, not the ones that do not. The real 404 mistake is wasting signals — when a removed page has backlinks, traffic, or a successor, a 301 redirect to the replacement preserves what a 404 discards.
How do 429 and 5xx errors affect crawling?
Googlebot reads 429 (Too Many Requests) and 5xx responses as a host in distress and cuts its crawl rate in response; when the errors persist, Google removes the affected URLs from the index. Recovery is symmetric — sustained clean 2xx responses bring crawling back.
The special case is robots.txt. When robots.txt itself answers 5xx, Google cannot confirm what it is allowed to crawl and temporarily treats the whole site as disallowed — crawling halts site-wide until the file serves a 200 again (or a 404, which Google reads as no restrictions). Monitor the response-code breakdown in the Crawl Stats report: a rising 5xx share is crawl capacity draining away.
Frequently Asked Questions
Do 404 errors hurt SEO?+
No. 404s for removed content are normal and carry no site-wide penalty. A 404 only costs you when the URL has backlinks, traffic, or a successor page — a 301 redirect preserves those signals; a 404 discards them.
Should I use 410 instead of 404?+
Use 410 when removal is deliberate and final: it drops the URL from the index marginally faster and ends Googlebot's rechecks sooner. The gap is marginal, so never leave dead URLs serving 200 while you decide.
Why did Googlebot stop crawling my site?+
Check robots.txt first: if it returns a 5xx error, Google temporarily treats the whole site as disallowed and crawling halts. The other common cause is sustained 5xx from the site itself, which cuts crawl rate and, if unresolved, deindexes pages.