Free the Inactive Memory Cache with `sudo purge`
Force macOS to discard cached file buffers after big file operations.
Run `sudo purge` to purge the disk cache, then check Activity Monitor for the change.
01Command
Command
$ sudo purge02What it does
macOS intentionally caches recently read files to speed later access, so “memory used” can look alarming while the cache is simply waiting to be reclaimed. `purge` asks the system to drop that buffer cache immediately. It is mostly useful for benchmarking or for memory-constrained servers running builds, not as an everyday booster.
03Risk
!Warning: Flushing cache makes the next file reads slower until it rebuilds — purging regularly usually hurts performance rather than helping it. Requires sudo.
04Undo
✓No undo needed — this command does not change persistent state.
05Sources
- purge(8) – force disk cache purgeEvidence: Manual page: purge attempts to purge disk buffer cache, per iOS/macOS memory pressure behavior
Last verified: 2026-09-18 · Category: System & Settings