Every time your browser loads a page, the server answers with a three-digit number before it sends a single byte of content. Most of the time that number is 200 — "everything's fine, here's your page" — and you never notice it. But when something goes wrong, or when a page has moved, those numbers are the only communication between the server and everyone trying to reach your site: browsers, Googlebot, link checkers, all of them.
If you run a website, you need to speak this language. Status codes are how you tell search engines "this page moved permanently" versus "this page is gone for good" versus "oops, the server crashed." Get them wrong and Google will misunderstand your intentions — sometimes for months.
Status codes are grouped by their first digit, and the grouping is all you need to remember the big picture:
For SEO, the codes that matter most live in the 3xx, 4xx, and 5xx families. Let's walk through the ones you'll actually encounter.
200 OK is what every page should return — the request succeeded and the content that follows is the real page. One thing to watch: misconfigured servers sometimes return 200 for pages that don't exist ("soft 404s"), which tricks Google into indexing garbage. Whenever you publish or move a page, verify it returns the code you intend — a server status checker takes seconds and should be part of your publishing routine, like proofreading a headline.
This family is the most SEO-critical, because redirects are how you preserve rankings when URLs change. 301 Moved Permanently = the page has a new permanent home; link equity passes and Google updates its index. 302 Found = the move is temporary; Google keeps the old URL indexed and doesn't transfer ranking signals. 307/308 are stricter versions preserving the request method — for ordinary pages, 301/302 cover it. 304 Not Modified is a caching optimization: "nothing changed, use your copy."
Redirect mistakes are silent ranking killers. Chains (A → B → C → D) dilute link equity and slow down crawling; loops (A → B → A) break the page entirely. After setting up any redirect, run both the old and new URLs through a WWW redirect checker to confirm each hop resolves to a single final 200 page with no chains.
404 Not Found is the famous one: the server works fine, but the page doesn't exist — a deleted page, a typo'd URL, a broken link. A few 404s are normal; hundreds from broken internal links waste crawl budget and frustrate visitors.
The right response to a 404 depends on the page. If it has a natural replacement, 301 it. If it's genuinely gone, let it 404 cleanly — don't redirect everything to your homepage (Google treats that as a soft 404 anyway). And make your 404 page useful: search box, popular links, a clear path back.
410 Gone is 404's more decisive sibling: the page is gone deliberately and won't come back. Google processes 410s faster than 404s, so use it when you're permanently removing content — it's the clearest "stop crawling this" signal you can send.
403 Forbidden means the server refuses the request — permission issues, blocked IPs, hotlink protection. If Googlebot gets 403s on pages it should crawl, those pages drop from the index.
401 Unauthorized is the login wall — expected on admin areas, a problem on public content. 429 Too Many Requests means rate limiting kicked in, usually from aggressive scrapers or misconfigured monitoring.
To find the 404s and other client errors hiding on your own site, run a crawl with a broken links finder — it surfaces every dead link on your pages so you can fix or redirect them. Our guide on how to find and fix broken links walks through the full cleanup process.
500 Internal Server Error is the generic "something broke on our end" — a crashed script, a bad plugin update, a misconfigured server. Visitors see an error page; Google sees a site it can't crawl.
502 Bad Gateway and 503 Service Unavailable usually mean an upstream problem — the reverse proxy can't reach the application server, or the server is temporarily overloaded or in maintenance mode. 504 Gateway Timeout is the same story with a clock: the upstream took too long.
Here's what most site owners don't realize: Google is patient with 5xx errors, but only up to a point. A few hours of downtime won't hurt you. Several days of persistent 500s, and Google starts dropping your pages from the index. If you're doing maintenance, return a proper 503 with a Retry-After header so Google knows to come back later.
Uptime monitoring plus a status code checker is the early-warning system. Check your homepage and key landing pages regularly — a server status checker takes seconds and tells you exactly what the server is saying before any content loads.
You don't need to memorize all sixty-odd status codes — just the dozen that affect real websites. Use 301 for permanent moves, treat 5xx as the emergency it is, and verify your codes the way you'd verify your content. Most "mysterious" SEO problems — pages that won't index, rankings that vanish after a migration — turn out to be status code problems once you look.
Check any URL's status code free with our Server Status Checker — see exactly what your server tells Google before a single byte of content loads.
A 301 is permanent: Google transfers ranking signals to the new URL and updates its index. A 302 is temporary: Google keeps the old URL indexed and doesn't pass full ranking value. Using 302 for a permanent move is one of the most common technical SEO mistakes — the new page may never rank properly.
Not inherently. Google expects sites to have some 404s, and they don't directly penalize you. They become a problem at scale — hundreds of 404s from broken internal links waste crawl budget and hurt user experience. Fix internal 404s; don't stress about external links you can't control.
No. Google treats mass redirects to the homepage as soft 404s — it figures out there's no real replacement and ignores the redirect. Redirect a deleted page to its closest relevant replacement, or let it return 404 (or 410 if the removal is deliberate).
Usually days to a few weeks for most pages, depending on crawl frequency. High-authority pages that Google crawls often get processed faster. If a 301 has been in place for months and Google still shows the old URL, check that the redirect is actually returning 301 (not 302 or a chain) and that the new page is crawlable.
Treat it as an emergency. Check your server error logs immediately — the cause is usually a recent change (plugin update, code deploy, config edit). If you need maintenance time, serve a proper 503 with a Retry-After header so Google knows to return. Persistent 500s lasting days can cause pages to drop from Google's index.
