Cargo Features

[dependencies]
wasm-bindgen-backend = { version = "0.2.99", default-features = false, features = ["std", "extra-traits", "spans"] }
default = std

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

std default
extra-traits

Enables extra-traits of syn

spans

wasm-bindgen-backend has 4 features without comments.