ShrinkCheck Changelog

Last updated: November 15, 2026

Up to version 0.9.x, the app was called CmpfsCheck.

v1.0.0 — 2026-11-15

Changed

CmpfsCheck is now ShrinkCheck. Your added items, history, settings, and folder permissions carry over.
The app is now free. The free trial period, license keys, and the January 1, 2027 lock on new compression are all gone.
The command-line call changed from open -a CmpfsCheck to open -a ShrinkCheck. If you set up automatic recompression with cron or similar, update the app name.
Compression actions are easier to find. The guidance bar at the top now offers Compress All, and you compress or decompress selected items from the bottom bar, the right-click menu, or the File menu. The per-row action column is gone.
The toolbar now has Space Recovery Wizard, Add, Filter, Storage Details, and Help (?) buttons, so you do not need to open a menu.
Savings are shown as "N% of original."
Until you select something, the bottom bar explains how to choose files or folders, then switches to Compress and Decompress.

Added

Self-check. The first time you open the app after a macOS or app update, it verifies with test files that compression and decompression work correctly. New compression does not start until it passes (decompressing, browsing, and searching always work).
Stop notices. The app periodically downloads public information from our website and, if a problem is found in your version, suspends new compression and explains why. Nothing is sent to the server, and you can turn the check off in Settings.
A guidance bar that shows the current state (self-check running, nothing added, checking, uncompressed items, all compressed, and so on) and the next button to press.
Right after launch, the totals from the last check appear immediately in a lighter color and are replaced as fresh checks finish.
English.
A notice when a newer version is available.
Exit codes 2, 3, and 4 for command-line automatic recompression (stopped by a notice, self-check failed, and so on), with a self-check before compressing.
Run Compression Self-Check in the Help menu.
Files skipped because another app was using them are shown in the summary and the history.
Failures such as low disk space, missing permissions, read-only volumes, and unsupported volumes are each explained with the cause and what to do.
If the old CmpfsCheck.app is still in your Applications folder, the app suggests deleting it (it never deletes it for you).
Folder icons show whether a folder's contents have been checked: a small spinner while checking, and a faded icon with a clock badge if not checked yet.
Compress After Check lets you queue a folder that has not been checked yet. That folder is checked first, and compression starts automatically when the check is done. You can keep working while you wait and cancel at any time.
A "What Is ShrinkCheck?" link on the empty window.

Performance

Fixed two causes of slow folder checks. An Xcode DerivedData folder with 68,000 files that took 41 to 50 seconds to check now takes about 2.3 seconds, with much less memory used while checking.
Right after launch, the list now updates folder by folder as each check finishes.
Compressing many files uses much less memory (compressing 160,000 files no longer adds about 1 GB while it runs).
Queuing a folder whose check has already finished no longer stops and restarts the check of another folder.

Fixed (safety)

Compressing a small file no longer changes its modification date.
Data over 16 KiB that does not shrink (photos, video, ZIP files, and so on) is no longer stored in compressed form, which used to increase disk usage slightly. If a file will not shrink, it is left untouched. Files already compressed by the old version stay as they are.
APFS clones (files that share their contents with the original) are no longer compressed, because compressing one of them would increase disk usage instead of reducing it.
A file that disappears just before processing is no longer counted as a failure.
Leftover temporary files (.slimtmp) are cleaned up safely, without removing ones still in use.
The old version's free trial records (including a hidden file named from your Mac's hardware UUID) are deleted on first launch.

v0.9.2 — 2026-08-22 (CmpfsCheck)

Extended the free period to the end of December 2026 (new compression locks on January 1, 2027, 00:00 JST; decompressing, browsing, and searching stay free).
Safety: files with resource forks are skipped; changes made by other apps during processing are no longer overwritten; temporary file name collisions are handled safely; restored sizes are verified on decompression; error messages explain the cause and what to do.
Performance: smoother scrolling during scans with many files; search stops when its sheet closes; volume information in Storage Status loads in the background.

v0.9.1 — 2026-06-14 (CmpfsCheck)

Shows About automatically on first launch, and adds a Select All button to the bottom bar.
Files of 16 MiB or more are compressed in a streaming fashion, so memory use no longer depends on file size; the file size limit setting was removed (files under 2 GiB, the decmpfs limit, are eligible).
Heavy folder scanning moved to the background, with a progress bar.

v0.9.0 — 2026-06-06 (CmpfsCheck)

First public release: a utility for using APFS transparent compression (decmpfs / LZFSE) safely from a window, with atomic replacement, SHA-256 round-trip checks, the Space Recovery Wizard, search, and command-line recompression for cron.

Old downloads: CmpfsCheck-0.9.2.dmg / 0.9.1 / 0.9.0 (these cannot compress new files after January 1, 2027; please use ShrinkCheck instead).