cargo build --no-default-features: build without the default feature set

cargo build --no-default-features builds the selected packages without the features listed under default in their [features] table. Combine it with --features a,b to build an exact subset, for example a minimal or no_std configuration, or to check in CI that the crate still compiles without its optional parts. The same flags work for cargo run, cargo test, cargo check and cargo doc.

Effect on cfg(feature)

The crate has a color feature that is on by default:

cargo new -q --vcs none app && cd app
cat >> Cargo.toml <<'EOF'

[features]
default = ["color"]
color = []
json = []
EOF
cat > src/main.rs <<'EOF'
fn main() {
    println!("color: {}, json: {}", cfg!(feature = "color"), cfg!(feature = "json"));
}
EOF
echo "--- default"
cargo run -q
echo "--- --no-default-features"
cargo run -q --no-default-features
echo "--- --no-default-features --features json"
cargo run -q --no-default-features --features json
echo "--- --all-features"
cargo run -q --all-features

--- default
color: true, json: false
--- --no-default-features
color: false, json: false
--- --no-default-features --features json
color: false, json: true
--- --all-features
color: true, json: true

Code behind #[cfg(feature = "color")] is compiled only when the feature is active, so each run produces a different binary.

Feature flags

For dependencies: default-features = false

The command-line flag does not reach dependencies. Turn off a dependency's defaults in Cargo.toml:

[dependencies]
serde_json = { version = "1", default-features = false, features = ["alloc"] }

cargo add serde_json --no-default-features --features alloc writes the same entry; see cargo add with features.

Pitfalls

• Feature unification. Features are additive across the whole dependency graph. If another crate depends on serde_json with defaults, default-features = false in your entry has no effect. Inspect it with cargo tree -e features -i serde_json.
• Untested combinations. A crate that only ever builds with defaults often breaks with --no-default-features. Add a CI job that runs cargo check --no-default-features (tools such as cargo-hack test every combination).
• Workspaces. In a workspace with resolver 2 or later, the flags apply to the packages selected with -p or the current directory, not to every member.
• A misspelled feature name fails the build with the package 'app' does not contain this feature, so typos do not pass silently.

Release builds are orthogonal to features: cargo build --release changes the optimisation profile, not the feature set.

FAQ