Location for Cache: Choose a folder where you would like Photo Mechanic to store cached thumbnails. On macOS, we recommend you use the default. Otherwise, you may need to tell Spotlight to ignore your cache location in order to speed up performance. 

Disk Cache Size: Maximum size of the cache folder. Generally, bigger is not always better, and the usefulness of the cache will top out at a few thousand MB. After that, you may see overly long startup and shutdown times. 

Reserve at least: Makes sure that there is always this amount of space left on the cache disk volume.

Empty on Quit: Empties the cache when Photo Mechanic is closed. Photo Mechanic generates thumbnails and previews quickly so it is not necessary to keep the cache between sessions. On quit, if emptying the disk cache takes longer than one and a half seconds, a progress dialog is displayed.

Remove Cached files that are older than: Cached files older than the specified number of days are removed as Photo Mechanic starts up. Keeping a large cache between sessions can cause Photo Mechanic to launch slower than normal because it has to check every cached file for its creation date on startup.

Memory Cache Size: Sets aside an amount of RAM to be used for caching and previewing. We recommend around 10% of your available RAM. 

Sort Cache: Photo Mechanic can cache the sorting of large folders to improve performance when re-opening the folder later on. To save disk space, PM will clear out older cached data per your choice of size here. You can also Empty Now to immediately get rid of cached sorting data.