Cargo Features

[dependencies]
std-next = { version = "0.1.1", default-features = false, features = ["std", "alloc", "unstable"] }
default = std

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

std default = alloc

Enables std of simdutf8

simdutf8:

enable CPU feature detection, on by default, turn off for no-std support

alloc std
unstable

std-next has 4 features without comments.