Free: check every pinned version in a lockfile against the malicious-package feed.

No auth, IP rate-limited. Send a package-lock.json, yarn.lock (v1/Berry), or pnpm-lock.yaml (v5/v6/v9), raw or as {"lockfile":"<contents>"}, or an explicit {"packages":[{"name","version"}]} list. Only EXACT versions are checked: a range has no definitive answer, because a compromised release usually sits between clean ones. Fail-closed: anything that could not be checked is listed in unverified, so an empty malicious list is only an all-clear when unverified is empty too. skipped counts entries with no registry identity (file:/link:/workspace:/git), which are reported rather than silently dropped.