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426 Upgrade Required

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

Original source

HTTP 426 Upgrade Required is a 4xx client error status code in the IANA HTTP Status Code Registry.

  • Code: 426
  • Reason phrase: Upgrade Required
  • Class: 4xx (Client Error)
  • Defined in: RFC 9110, Section 15.5.22

Source and provenance

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

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Version history

  1. Published by Koskamo

    Version 1

426 Upgrade Required — Koskamo