Consentful API Access

OptIn defines annotations that can be used by libraries and applications to require and to declare explicit opt-in into APIs.

Compile-Time Safety

OptIn provides tooling that enforces correct use of opt-in requirements at compile-time to ensure that unstable APIs are used intentionally.

Third-Party Compatibility

OptIn allows customizing it first-party tooling to integrate seamlessly with third-party libraries without opt-in support (e.g., Guava's @Beta).