How to clear Go cache on Mac, with go clean.

Where Go keeps its cache on a Mac

go env GOCACHE GOMODCACHE

Sizes are from one developer Mac with Go 1.26 in October 2026. The build cache follows the Mac convention and lives in ~/Library/Caches. The module cache lives under GOPATH, which is ~/go unless you've changed it. Set GOCACHE or GOMODCACHE with go env -w to move them.

go clean flags for every cache

go clean -cache        # the build cache
go clean -testcache    # only cached test results
go clean -modcache     # every downloaded module
go clean -fuzzcache    # inputs saved by go test -fuzz

• -cache removes compiled packages and cached test results. The next build compiles everything from source, which takes longer for big projects. Safe.
• -testcache keeps compiled code and only forgets test results, so go test runs every test again. Use it when a cached “ok” is hiding a flaky test; it frees almost nothing.
• -modcache removes the source of every module you've downloaded. The next build downloads them again, from the Go module proxy by default. Safe if you're online; vendored projects don't need it at all.
• -fuzzcache removes the inputs that fuzzing found interesting. Only clear it if you don't need to replay them.

Why go clean -modcache, not the Trash

Go makes every file in the module cache read-only, so nothing edits a dependency by accident. That's why moving ~/go/pkg/mod to the Trash fails partway, and rm -rf prints “Permission denied” over and over. go clean -modcache fixes the permissions and removes it cleanly. If you'd rather have a cache you can delete normally, build with -modcacherw, or add it to GOFLAGS.

The build cache has no such problem. You can move ~/Library/Caches/go-build to the Trash, though go clean -cache does the same thing.

How big Go caches get

Go trims its own build cache: entries unused for about five days are removed as you build. So the build cache stays at a few hundred megabytes to a few gigabytes; on the Mac above, it was 258 MB. The module cache is never trimmed. Each version of each module stays until you clear it, so a Mac that has built many projects over a few years can hold several gigabytes. The go toolchains Go downloads for toolchain lines in go.mod live in the module cache too, at a few hundred megabytes each.

Also writing Rust? See cargo clean. Or Homebrew, and every tool's cache.