Recognised as HTTP status
HTTP 503 Service Unavailable
- 503 Service Unavailable
- Server error
- RFC 9110
HTTP 503 Service Unavailable is a server error response: the server is overloaded or down for maintenance. It is defined in RFC 9110, and the server failed to fulfil an apparently valid request.
What it means
Status code503
Reason phraseService Unavailableadvisory only; clients must not depend on the wording
Class5xx Server error
MeaningThe server is overloaded or down for maintenance
Defined inRFC 9110
Cacheable by defaultNoonly cacheable if the response says so explicitly
How clients behave
Indicates an errorYes
Whose faultThe server
Body expectedUsually
Retry-After headerCommontells the client when to try again
Safe to retry automaticallyOften
The 5xx class
Class meaningThe server failed to fulfil an apparently valid request
Codes in this class11
Lowest in class500
Highest in class511
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