Apple has released macOS High Sierra.
macOS High Sierra is designed to improve on the previous macOS Sierra operating system with some major under-the-hood upgrades and a handful of outward-facing changes.
Apple File System (APFS), a file system designed for solid state drives, is the new default for these drives in macOS High Sierra. APFS is safe, secure, and optimized for modern storage systems. It features native encryption, safe document saves, stable snapshots, and crash protection, plus it brings performance improvements.
An interesting new feature in high Sierra that was only recently unveiled: the new version of macOS checks your Mac’s firmware against Apple’s own database once a week to see if it’s been tampered with.