---
type: "Specification"
title: "HTTP Message Signatures — RFC 9421"
description: "End-to-end integrity and authenticity across intermediaries."
resource: "https://www.rfc-editor.org/rfc/rfc9421"
tags: [http, integrity, security]
generated: { by: human:crpage, at: 2026-07-09T09:44:00Z }
status: stable
sources: [{ id: primary, resource: "https://www.rfc-editor.org/rfc/rfc9421" }]
---

Protects specific message components even through proxies and transformations. Useful for high-integrity requests, webhooks and regulated submission flows; not a full auth story on its own.