As a competitor to Picasa it packs a powerful punch as a slick OS X image management app that's fully integrated into iCloud, Maps and more. IPhoto is Apple's flagship application for managing and viewing photos on your Mac. If you're already running Yosemite, you can download Photos for Mac by checking for updates in the Mac App Store. iPhoto You can download its replacement, Photos for Mac, by upgrading to OS X Yosemite for free. UPDATE: Apple has discontinued support for iPhoto.
