The HTTP 417 Expectation Failed status code indicates that the server cannot meet the requirements specified in the Expect header.
Published 16 Jul 2026 · HTTP Status Code
The 417 Expectation Failed response occurs when a client sends an expectation that the server cannot satisfy.
The most common example is the Expect request header.
Expect: 100-continueThis can appear when debugging HTTP clients, proxies, and older server implementations.
417 Expectation Failed means the server cannot fulfil the expectations requested by the client.
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