The HTTP 503 Service Unavailable server error response code indicates that the server is not ready to handle the request.
Common causes are a server that is down for maintenance or that is overloaded. Note that together with this response, a user-friendly page explaining the problem should be sent. This responses should be used for temporary conditions and the Retry-After HTTP header should, if possible, contain the estimated time for the recovery of the service.
Caching-related headers that are sent along with this response should be taken care of, as a 503 status is often a temporary condition and responses should usually not be cached.
503 Service Unavailable
| Specification | Title |
|---|---|
| RFC 7231, section 6.6.4: 503 Service Unavailable | Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content |
| Feature | Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | Servo |
|---|---|---|---|---|---|---|---|
| Basic Support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |
| Feature | Android | Chrome for Android | Edge Mobile | Firefox for Android | IE Mobile | Opera Mobile | Safari Mobile |
|---|---|---|---|---|---|---|---|
| Basic Support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |
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https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/503