Cargo Features

[dependencies]
xiu = { version = "0.13.0", default-features = false, features = ["std"] }
default = std

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

std default = serde

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.

serde std