Cargo Features

[dependencies]
brightness = { version = "0.5.0", default-features = false, features = ["async"] }
default = async

The async feature is set by default whenever brightness is added without default-features = false somewhere in the dependency tree.

async default = async-trait, blocking, futures

Features from optional dependencies

In crates that don't use the dep: syntax, optional dependencies automatically become Cargo features. These features may have been created by mistake, and this functionality may be removed in the future.

async-trait async
blocking async
futures async