What Is actions/cache in GitHub Actions?

actions/cache saves and restores directories between runs by key, so you do not re-download dependencies every time.

Installing dependencies on every run is slow and wasteful. actions/cache persists chosen directories keyed on something like a lockfile hash, restoring them on the next run for a big speedup.

What it is

The official caching action. You give it a path to cache and a key; on a hit it restores the path, and at job end it saves the path under that key on a miss.

Caching npm

steps:
  - uses: actions/cache@v4
    with:
      path: ~/.npm
      key: npm-${{ hashFiles('package-lock.json') }}
      restore-keys: npm-

How it works

At the start of the job the action looks for an exact key match, falling back to restore-keys prefixes. If nothing matches, the job runs normally and the path is uploaded as a new cache entry afterward.

Choosing a good key

Keys usually hash a lockfile so the cache invalidates only when dependencies change. restore-keys provide partial fallbacks so you still get most of a stale cache after a small change.

Why it matters

Caching can cut minutes off every run, which directly lowers cost. Many setup-* actions have built-in caching, but actions/cache covers anything else. Latchkey managed runners add their own layer caching on top for even faster builds.

Related concepts

Caching differs from artifacts: caches speed up future runs, artifacts share outputs of the current run.

Key takeaways

actions/cache restores and saves paths by key.
Hash a lockfile for the key; use restore-keys for fallback.
Caches speed up runs and lower cost.