Tip: If Safari or other applications keeps crashing because of insufficient storage on your Mac, you can also use MacMaster to clean up the Mac and free up more space. Now you can open Safari and see if it crashes or hangs again. Click Clean to delete cookies, internet history, download history of Safari on your Mac.It is the primary operating system for Apple's Mac computers. macOS (/ ˌ m æ k oʊ ˈ ɛ s / previously Mac OS X and later OS X) is a series of proprietary graphical operating systems developed and marketed by Apple Inc.