How to Handle Feature Flags in Published Crates

Cargo
2026-04-17T12:05:42+00:00
Define optional features in Cargo.toml and wrap code with #[cfg] attributes to conditionally compile them.

Handle feature flags in published crates by defining them in Cargo.toml and using #[cfg(feature = "flag_name")] to conditionally compile code. Add the feature definition to your Cargo.toml file and wrap the conditional code in your source files with the attribute.

[features]
default = []
my_feature = []

#[cfg(feature = "my_feature")]
pub fn enabled_function() {
    println!("Feature is active");
}
  1. Define the feature in Cargo.toml under the [features] section.
  2. Wrap the code block in your .rs file with #[cfg(feature = "my_feature")].
  3. Users enable the feature by adding my_feature = true to their dependency declaration.