macOS High Sierra added support for HEVC, a more efficient video codec that allows for smaller file sizes without sacrificing video quality.
In the original 10.13 release, converting a Fusion Drive (a hybrid SSD+HDD setup) to APFS could result in data loss or an unbootable system. 10.13.1 explicitly disabled automatic APFS conversion for Fusion Drives and older rotational hard drives. Instead, the installer would leave those drives as HFS+ (Mac OS Extended) unless manually converted via Disk Utility after a full backup. macos high sierra 10.13.1
A subtle but welcome change: the Setup Assistant was updated to properly clean up temporary files after migrating data from Time Machine or another Mac. In 10.13.0, some users experienced leftover “.cleaned” folders consuming gigabytes of hidden storage. macOS High Sierra added support for HEVC, a