cargo clean on Mac, and what it misses.

Where Cargo keeps its cache on a Mac

Cargo's home is ~/.cargo, or wherever CARGO_HOME points. Build output doesn't go there: it goes in a target folder inside each project.

Rust isn't installed on the Mac this page was written on, so there are no measured sizes here. Check yours with:

du -sh ~/.cargo/registry ~/.cargo/git 2>/dev/null
find ~ -name target -type d -prune -exec du -sh {} + 2>/dev/null | sort -h | tail -20

Not every folder named target is Rust's: check for a Cargo.toml beside it before you delete one.

What cargo clean deletes

cargo clean                  # the whole target folder
cargo clean --release        # only target/release
cargo clean --doc            # only target/doc
cargo clean -p some-crate    # one package's artifacts

cargo clean removes compiled dependencies, incremental compilation data, and your binaries for that one project. It's safe: cargo build makes it all again, which can take minutes for a project with many dependencies. It doesn't touch ~/.cargo.

Why target gets so big: it keeps separate builds for debug and release, for every target triple you build, and incremental data for every crate. Changing compiler versions or features adds more rather than replacing. A medium project's target folder is often several gigabytes, and tens of gigabytes isn't unusual.

How to clear Cargo cache in ~/.cargo

• registry/cache: safe. The compressed .crate file for every crate version you've downloaded.
• registry/src: safe. Those crates unpacked. Cargo unpacks them again from the cache, or downloads them.
• git: safe. Clones of dependencies that point at a git repository. Cargo clones them again.
• bin: keep. cargo, rustc shims from rustup, and everything you installed with cargo install.

Cargo has no stable command to clear its home folder, so moving those folders to the Trash is the usual way. Do it with no build running. Toolchains themselves live in ~/.rustup/toolchains; remove old ones with rustup toolchain uninstall.

How big the Cargo cache gets

Less than it used to. Since Rust 1.88, Cargo cleans its own cache automatically: it removes downloaded files it hasn't used in three months, and unpacked files it hasn't used in one month. So ~/.cargo/registry usually holds a gigabyte or two. The target folders are another story: nothing cleans those, so ten old projects can mean tens of gigabytes. cargo-sweep, a third-party tool, can remove only the stale parts of a target folder if you'd rather not rebuild from scratch.

Also writing Go? See go clean -cache. Or Gradle, and every tool's cache.