{
 "id": "rfc-9421",
 "name": "HTTP Message Signatures",
 "aliases": [
  "RFC 9421"
 ],
 "definition_md": "A way to sign chosen components of an HTTP message so a server can verify the sender, defined in RFC 9421. Web Bot Auth uses it to let a crawler or agent prove who it is.",
 "step": "identify",
 "related_protocols": [
  "http-message-signatures",
  "webbotauth"
 ],
 "sources": [
  {
   "url": "https://www.rfc-editor.org/rfc/rfc9421",
   "date": "2026-10-15",
   "label": "VERIFIED"
  }
 ],
 "part_of": null,
 "group": null,
 "url": "https://agenticweb.wiki/terms/rfc-9421/",
 "category": "identify",
 "type": "term"
}