GlossarySEO
What is a 5xx server error?
Also called: 500 error, 502 bad gateway, 503 service unavailable, server error
Definition
A 5xx server error is any HTTP status from 500 to 599, meaning the server failed to handle a valid request. Google slows its crawling when it sees them, and persistent errors can drop pages.
5xx server error, explained
The common ones: 500 Internal Server Error (the app crashed), 502 Bad Gateway and 504 Gateway Timeout (a proxy or CDN couldn't reach your origin), and 503 Service Unavailable (the server is overloaded or down for maintenance). To a crawler they all say the same thing: try later.
Google's documentation says 5xx errors and 429 prompt its crawlers to temporarily slow down, and that crawl rate gradually increases once the server returns 2xx again. Search Console lists affected URLs as "Server error (5xx)" in the Page indexing report. The Crawl Stats report shows host status, which tells you whether availability problems affected crawling across the site.
Short outages are fine. Long ones are not. Google's guidance on pausing a site says a 503 is only suitable for a day or two, and that keeping a site unavailable longer risks URLs being removed from the index, with no fixed recovery time. For planned maintenance, return 503 with a Retry-After header rather than a 200 maintenance page, which could get indexed in place of your content.
On serverless and edge platforms, intermittent 5xx errors often come from timeouts on heavy pages, cold starts or a failing upstream API. Prerendering important pages as static HTML removes most of these failure paths.
Why it matters for founders
A young site with limited crawl attention can't afford Googlebot backing off. Repeated 5xx errors mean new pages get discovered later and existing ones get refreshed less often.
Example
Your blog pages are rendered on each request and call a CMS API. When the CMS is slow, pages time out with 504. You switch them to static generation with periodic revalidation, and server errors disappear from Search Console.
Common mistakes
- Serving a maintenance page with status
200. - Leaving a site on
503for a week during a migration. - Ignoring intermittent 5xx errors because the page loads when you check it.
- Rate-limiting Googlebot with
403instead of429or503.
Sources
- Google Search Central: How HTTP status codes and network errors affect Google Search
- Google Search Central: Pause or disable a website
- Search Console Help: Page indexing report
Checked
Related terms
- HTTP status codeAn HTTP status code is the three-digit number a server sends back with every response, like
200,301,404or503. It tells browsers and crawlers whether the request worked, moved, failed or should be retried. - Crawl Stats reportThe Crawl Stats report in Google Search Console shows how Googlebot crawled your site over the past 90 days: total requests, download size, average response time, host status, and breakdowns by response, file type and purpose.
- Crawl budgetCrawl budget is the set of URLs Google can and wants to crawl on your site in a given period. It depends on how much your server can handle and how much Google wants your pages.
- Static site generation (SSG)Static site generation (SSG) builds each page's HTML once, at build time, and serves the same file to every visitor. It's the fastest and most reliable way to give crawlers complete pages.