In a giant monorepo, you often only care about one subdirectory. Sparse checkout keeps the working tree small.
Modern syntax (cone mode, faster):
git clone --no-checkout https://github.com/big/monorepo
cd monorepo
git sparse-checkout init --cone
git sparse-checkout set apps/web tools/scripts
git checkout
Now only apps/web and tools/scripts exist on disk; everything else is invisible. Git operations stay fast.
Disable:
git sparse-checkout disable
Combine with --filter=blob:none (next lesson) for genuinely huge repos — you skip downloading old blobs entirely.