opaquetoken

opaquetoken refers to a type of security access token whose contents are not intended to be read by the client. In contrast to self-contained tokens such as JSON Web Tokens (JWTs), an opaquetoken reveals no meaningful information when decoded by the client; its value is typically a random string.

How it works: when a resource server receives an opaquetoken, it cannot interpret the token locally. Instead, the server validates the token by contacting the authorization server via a token introspection endpoint (as described in OAuth 2.0 Token Introspection). The introspection response is a structured object that may include fields such as active status, scope, subject, issuer, and expiration time. If the token is valid, the resource server enforces access according to the returned metadata.

Advantages: opaque tokens reduce leakage of internal claims to clients, since the token itself carries no readable data. They simplify token rotation and revocation at the authorization server, and support centralized policy enforcement. This can enhance privacy and control in certain architectures.

Disadvantages: their validation requires a live network call to the authorization server, introducing latency and a potential single point of failure. Scalability concerns can arise in high-throughput systems unless introspection is efficiently implemented and cached.

Use cases: opaquetokens are common in enterprise and microservices environments where clients are not trusted with sensitive claims or where centralized access control and revocation are priorities. They are widely used alongside OAuth 2.0 and OpenID Connect ecosystems, particularly when self-contained tokens are undesirable.

See also: OAuth 2.0, Token introspection, opaque access token, JSON Web Token, OpenID Connect.