The server is temporarily unable to handle requests. It might be overloaded, undergoing maintenance, or just needs a moment to recover.
Your website gets a sudden traffic spike from a viral post and the server can not handle all the concurrent connections.
A 503 Service Unavailable with a `Retry-After` header tells Googlebot to come back later — Google respects this and won't deindex your pages for planned maintenance. Without Retry-After, sustained 503s will cause deindexing.
For planned maintenance, return 503 with `Retry-After: 3600` (seconds until you're back). For unexpected 503s, scale your server capacity, add a CDN in front, or implement a queue. Monitor traffic spikes with uptime tools.
Check how any URL responds in real time