Fix: Mac Clear Preview Cache

Resolve Mac OS X Preview Application issues including crashing or unsaved changes. You can run these Terminal commands to clear Preview cache and recent items.

1. Quit Preview. 

2. Open Terminal on Mac OS X (Application -> Utilities -> Terminal)

3. Type the following commands in Terminal. (You can copy and paste)

defaults delete com.apple.Preview.LSSharedFileList RecentDocuments
defaults write com.apple.Preview NSRecentDocumentsLimit 0
defaults write com.apple.Preview.LSSharedFileList RecentDocuments -dict-add MaxAmount 0
killall Dock

4. Re-launch Preview for Mac and you should have a clean slate again. It should no longer crash if you were frequently using Preview viewing and editing photos.