Articles/HTTP

HTTP 417 Expectation Failed — What It Means

What HTTP status code 417 Expectation Failed means, when servers return it, and how to handle it correctly.

Published September 25, 2026

HTTP 417 Expectation Failed — The server can't meet the requirements of the Expect header.

Key points

  • Returned when a client sends an "Expect: 100-continue" header and the server refuses to honor it
  • Rare in modern HTTP usage since most clients handle this transparently
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