The expectation given in the Expect header cannot be met by the server.
Quick facts
When does it occur
The expectation given in the Expect header cannot be met by the server.
It belongs to the 4xx Client Error class of responses, defined in RFC7231#6.5.14.
Browse all codes in this class: 4xx Client Error
Common causes
Frequently asked questions
417 belongs to the 4xx Client Error class and is generally not cached for long; behavior is controlled by Cache-Control.
4xx Client Error: The expectation given in the Expect header cannot be met by the server.
Sources & standards
Updated 2026-08-18
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