Cargo Features

futures-io = { version = "0.3.30", default-features = false, features = ["std", "unstable"] }
default = std

The std feature is set by default whenever futures-io is added without default-features = false somewhere in the dependency tree.

std default

Unstable features These features are outside of the normal semver guarantees and require the unstable feature as an explicit opt-in to unstable API.