PixelSnap is a macOS measuring tool that lets designers and developers grab pixel-perfect measurements of anything on screen — UI elements, screenshots, mockups, native apps. Drag from one point and it instantly snaps to the edges of the closest visible element, so you don't have to fiddle with rulers.

Version 2 added smart guides, a screen ruler, a color picker, distance-to-edge measurements, multi-monitor support and an integration with CleanShot X for measured screenshots. Made by MTW (the team behind CleanShot X), PixelSnap is a paid macOS app available on the standalone site and through Setapp.