Apple has now released macOS 10.13 High Sierra via the Mac App Store for Macs running at least OS X 10.8 Mountain Lion, going back to the MacBook and iMac from late 2009 and the MacBook Air, MacBook Pro, Mac mini, and Mac Pro from 2010. (These are the same hardware requirements as for 10.12 Sierra.) As we noted at the very start of our WWDC coverage in “” (5 June 2017), High Sierra is one of Apple’s smaller upgrades in the recent “tick, tock” of operating systems, including Leopard/Snow Leopard, Lion/Mountain Lion, Yosemite/El Capitan, and now Sierra/High Sierra.
However, as much as High Sierra has relatively few user-facing changes and new features, Apple is using the release to make some huge updates under the hood. High Sierra automatically converts Macs with SSDs to the new APFS file system (see “HEVC and HEIF Will Make Video and Photos More Efficient,” 30 June 2017). These infrastructural changes should modernize the Mac’s underpinnings, improve performance, reduce storage needs, and pave the way for future improvements.,” 24 June 2016) and uses the new HEVC and HEIF formats for videos and photos (see “
The significance of those changes raises the question: when should you upgrade your Mac to High Sierra? With iOS, and even more so with watchOS and tvOS, we generally trust Apple enough to upgrade quickly, in large part because the company exercises such control over those operating systems that they can’t vary much. Plus, frankly, problems with an Apple Watch or Apple TV aren’t likely to impact your life much.
On a Mac, though, there are innumerable opportunities to stray from the straight and narrow, and many users do. If developers follow Apple’s rules, and if Apple did its due diligence during beta testing, there should be no problem with upgrading to High Sierra. But there’s no way to know if the hardware and software on your Mac meet Apple’s specs, or if Apple was able to test your particular configuration. That doesn’t mean anyone failed to do their jobs right; it’s just a fact. Add that to the fact that many of us rely heavily on our Macs to get our jobs done, and the upgrade question becomes all the more important.
Happily, if you follow Joe Kissell’s advice in “” and make a bootable duplicate right before upgrading, you have nothing to lose except perhaps time. That’s because, in the worst case scenario, you can always reformat your Mac’s boot drive and restore from your bootable duplicate. Joe has released the 1.1 version of his book now, and it includes instructions for downgrading if necessary.
That said, there’s no harm in waiting, and High Sierra doesn’t have so many features as to make the upgrade immediately compelling (for an in-depth guide to what’s new, and much more, see Scholle McFarland’s “”). If you fall into one of three main groups of users, we recommend holding off on High Sierra for at least a few weeks, or until 10.13.1 comes out with the usual bevy of bug fixes:
If you can’t spare the time to deal with unanticipated problems. That’s true if you’re upgrading your own Mac or if you’re upgrading the Macs of users who you support (see “,” 11 September 2017).
If you’re uncomfortable with the tasks involved with downgrading despite Joe’s advice.
If some piece of software you rely on is incompatible with High Sierra. Developers are releasing updates, but older versions of apps may experience problems.
Users of one particular class of software should delay upgrades: those who rely on disk utilities that haven’t yet been upgraded to be compatible with APFS. You really don’t want to let an old disk utility touch an APFS-formatted drive. That could also be true of backup software. Although the developers of and  have said that they’re ready for APFS, the developers behind  have expressed more worry due to minimal documentation from Apple (nonetheless, SuperDuper 3.0B1 is available for testing).
If you do upgrade to High Sierra, make sure to maintain a Time Machine backup, since Apple has undoubtedly used its internal knowledge about APFS to update Time Machine as necessary. Up-to-date backups protect you from a multitude of evils.
Now, despite these words of caution, if you’ll excuse me, I need to finish going through Joe’s checklists so I can upgrade my main iMac.