Cargo Features

[dependencies]
indexed_vec = { version = "1.2.1", default-features = false, features = ["serial"] }
default = serial

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

serial 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 serial