Articles/HTTP

HTTP 503 Service Unavailable — What It Means

What HTTP status code 503 Service Unavailable means, when servers return it, and how to handle it correctly.

Published September 26, 2026

HTTP 503 Service Unavailable — The server is temporarily unable to handle the request.

Key points

  • Typically caused by server overload, planned maintenance, or a dependency being temporarily unreachable
  • Should include a Retry-After header telling clients when to try again
  • Distinct from 500 in that it implies a temporary condition rather than a bug
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