Overview
- Proof launched x401 on Friday, June 26, 2026, publishing the specification, implementation materials, and live demos at x401.id.
- The protocol is issuer-neutral so services can accept credentials from governments, companies, or decentralized issuers while choosing which issuers and claims they trust.
- x401 extends HTTP authentication to let agents respond to 401-style challenges with cryptographically signed Verifiable Credentials that support selective disclosure and zero-knowledge proofs.
- Major firms including Circle, OpenAI, Google, and Okta contributed to the specification, and Circle says it will pair x401 with the x402 payments standard as an early adopter and co-endorser.
- Proof demonstrated an initial deployment through its Digital ID and cloud wallet that uses NIST IAL2-grade proofing, Kantara certification, and a WebTrust-audited CA, and the company plans to submit x401 to the FIDO Alliance for standards review while broader multi-issuer adoption remains nascent.