HTTP 503 Service Unavailable

What 503 means

Usually due to maintenance or overload. A Retry-After header can say when to try again.

Common causes

• Planned maintenance.
• Traffic overload or exhausted server resources.
• Auto-scaling that has not caught up.

How to fix it

1. Wait and retry.
2. Scale server capacity or add caching.
3. During maintenance, return 503 with Retry-After.

SEO impact

503 with Retry-After is the correct response for planned maintenance; search engines retry instead of dropping pages.

How to check a status code

Enter a URL in the HTTP Status Checker to see its status code, every redirect hop, and response time. For redirect-heavy pages, the Website Speed Test shows how much time redirects add.

FAQ

What does HTTP 503 mean?

503 Service Unavailable is a 5xx server error status code. The server is temporarily unable to handle the request.

What causes a 503 error?

Planned maintenance. Traffic overload or exhausted server resources. Auto-scaling that has not caught up.

How do I fix HTTP 503?

Wait and retry. Scale server capacity or add caching. During maintenance, return 503 with Retry-After.