503 Service Unavailable

What is HTTP 503?

This status code indicates that the server is currently unable to handle the request due to temporary overloading or scheduled maintenance. The implication is that this is a temporary condition and the server will be available again soon. The server should send a Retry-After header indicating when the client should try again. Search engines understand this code means the downtime is temporary and will not deindex the URL.

Defined in RFC 9110

Common Causes

• The server is undergoing planned maintenance or a deployment
• Traffic spikes overwhelming the server's capacity to handle requests
• A dependent service like a database or cache is temporarily unavailable
• Auto-scaling has not yet provisioned enough instances to handle current load

How to Fix

• Check the Retry-After header and wait before retrying the request
• If you operate the server, check resource usage, scale capacity, or address the overload
• Verify that all dependent services like databases and caches are operational
• Implement a maintenance page with the 503 status code during planned downtime for proper SEO handling