Macs always perform great out of the box, but over time they can start to feel slower and more sluggish. The reasons for that can seem mysterious, but often they're easy-to-fix if you can figure out what's gone wrong. That's where performance monitoring comes in! There are a lot of great performance monitoring tools for your Mac, but it can be tough sorting the really great ones from garbage. That's where iMore comes in! Here are the best apps for monitoring your Mac's performance!