Released in 2017, High Sierra was a refinement release — Apple's chance to rebuild macOS from the foundation up, without changing the view from the surface. Same familiar desktop, an entirely new engine underneath.
A new file system
High Sierra's biggest change was invisible: it quietly replaced HFS+ with APFS (Apple File System) on SSDs, built for flash storage from the ground up. That brought native encryption, faster directory sizing, and space-efficient snapshots that made backups and cloning far quicker.
Metal 2 & graphics
Apple's graphics framework got a major update in Metal 2, giving apps closer access to the GPU for smoother rendering. It laid the groundwork for external GPU support and VR development on the Mac for the first time.
Smarter Photos
The Photos app was reworked with a redesigned sidebar, new editing tools for curves and selective color, and deeper syncing with third-party editors — while still organizing memories the way earlier versions did.
Compression & efficiency
HEVC (H.265) video and HEIF image formats arrived here, cutting file sizes roughly in half compared to their predecessors without a visible drop in quality — a change felt most on storage-limited Macs.
Compatibility
High Sierra supports a wide range of older Macs — many models from 2010 onward — which made it a popular stop for keeping legacy hardware secure and usable long after newer macOS versions dropped support for them.
Official Apple Support page — installs via the Mac App Store.