HTTP 503 — Service Unavailable

The server is currently unavailable

When to use it

Use status 503 when this is the correct HTTP response semantic: The server is currently unavailable

Request and response example

GET /maintenance HTTP/1.1
Host: api.example.com

HTTP/1.1 503 Service Unavailable
Retry-After: 120

Related status codes

500, 501, 502, 504

References

MDN · RFC 9110