Client error · HTTP reference

412Precondition Failed

A condition in the request headers evaluated to false.

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A condition in the request headers evaluated to false.

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Returns this HTTP status with the current sponsor’s name, advertising message and website. Useful for testing how your app handles a response.

This is an independent project. Sponsorship does not confer ownership of HTTP standards.

Client error responses explain why a request could not be fulfilled.

Check the URL, method, authentication and request content. Repeating the same request without addressing the cause may produce the same response.

Reference reviewed 5 September 2026. How we use sources.