A 503 Service Unavailable status code indicates that a server is temporarily unable to handle a request, commonly used deliberately during planned maintenance to tell search engines the downtime is temporary and the site should not be deindexed.
Properly implementing a 503 status during maintenance, ideally paired with a “Retry-After” header, helps prevent search engines from interpreting temporary downtime as a permanent site failure that could trigger a drop in rankings.
A common mistake is leaving a site in maintenance mode without a proper 503 status for an extended period, which can eventually cause search engines to deindex previously ranking pages.
Proper handling of planned downtime is part of our Technical SEO service.