400 Bad Request

Document v1 · published by Koskamo · updated 2026-10-04

HTTP 400 Bad Request is a 4xx client error status code in the IANA HTTP Status Code Registry.

Code: 400
Reason phrase: Bad Request
Class: 4xx (Client Error)
Defined in: RFC 9110, Section 15.5.1

Source and provenance

Original source: www.iana.org
Published on Koskamo by: Koskamo
Citation version: Document v1
Reuse: IANA HTTP Status Code Registry (iana.org/assignments/http-status-codes); registry data reproduced verbatim with references

The original source supplies the underlying information. Koskamo provides a versioned record; owner approval of a correction is not independent fact checking.

The IANA registry identifies the registered status code and its specification. Follow that specification for protocol behavior; individual applications can add their own response details.

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Version history

Published by Koskamo2026-10-04
Version 1