cargo-machete is a Cargo tool that detects unused dependencies in Rust projects, in a fast (yet imprecise) way.

See also the blog post for a detailed writeup.

Install cargo-machete with cargo:

cargo install cargo-machete

Run cargo-machete in a directory that contains one or more Rust projects (using Cargo for dependency management):

cd my-directory && cargo machete

# alternatively

cargo machete /absolute/path/to/my/directory

The return code gives an indication whether unused dependencies have been found:

• 0 if machete found no unused dependencies,
• 1 if it found at least one unused dependency,
• 2 if there was an error during processing (in which case there's no indication whether any unused dependency was found or not).

This can be used in CI situations.

To ignore a certain set of dependencies in a crate, add package.metadata.cargo-machete to Cargo.toml, and specify an ignored array:

For example:

[dependencies]
prost = "0.10" # Used in code generated by build.rs output, which cargo-machete cannot check

[package.metadata.cargo-machete]
ignored = ["prost"]

If there are too many false positives, consider using the --with-metadata CLI flag, which will call cargo metadata --all-features to find final dependency names, more accurate dependencies per build type, etc. ⚠ This may modify the Cargo.lock files in your projects.

We welcome community contributions to this project.

MIT license.