Security

OAuth 2.1

The modern auth-delegation flow: code + PKCE for everyone.


In plain terms

Removes implicit and password grants. Adds mandatory PKCE, exact-match redirect URIs, refresh token rotation.

Origin

Aaron Parecki and Dick Hardt began consolidating OAuth 2.0 + ten years of security errata into OAuth 2.1 in 2020. Still draft at IETF, but most modern OAuth libraries already implement its rules.

Where it shows up in production
  • PKCE everywhere Previously only mobile/public clients; now confidential clients use it too.
  • No implicit / no password grants Both grant types are deprecated. Only authorization-code-with-PKCE and client-credentials remain.
On Semicolony
Sources & further reading
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