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By Jason Snell

Apple activates warning for users of 32-bit apps in High Sierra

Note: This story has not been updated for several years.

Apple’s long transition away from 32-bit software takes another step beginning April 12. When the clock strikes the witching hour (local time), Macs running macOS 10.13.4 will display a warning the first time any non-Apple app that isn’t 64-bit compliant is opened.

The warning, which reads “[App name] is not optimized for your Mac,” will only appear once per app, and will direct users to an Apple knowledge base article to learn more about the situation.

Apple alert

For years, Apple has been migrating its hardware and software from the older 32-bit approach, with 64-bit apps having access to more memory and allowing faster, more efficient system performance. Many of the newest core features of the Mac, including the Metal graphics acceleration architecture, are designed with 64-bit in mind and only work with 64-bit apps.

Though this new wrinkle will expose the migration to Mac users for the first time, it’s just the latest in an ongoing series of transitional steps. Users of 32-bit iOS apps were warned in late versions of iOS 10 that their apps were deprecated, and iOS 11 won’t run 32-bit apps at all.

Mac developers were told at Apple’s developer conference last year that macOS High Sierra would be the “last version of macOS to run 32-bit apps without compromise,” and many of them have been busy updating their apps to be fully 64-bit compatible. Just a couple of months ago BBEdit, one of my favorite Mac apps, updated to 64 bit.

To get a complete list of your 32-bit apps, open the System Report app by choosing About This Mac from the Apple menu and clicking the System Report button. Click on Applications under Software in the sidebar, and you’ll be presented with a list of all the apps on your Mac. One of the columns in that list is “64-bit (Intel)”, and if an app’s entry says “No”, you will be warned if you launch it. (Unless it’s from Apple, which is apparently exempt from warnings.)

What does this mean for my favorite 32-bit app?

For now, nothing. The one-time alert is the only thing that’s new in macOS 10.13.4 on this front. 32-bit apps aren’t behaving any differently now than they did last week or last month.

While Apple hasn’t detailed exactly what “without compromise” means, it’s my understanding that 32-bit apps will run on the successor to High Sierra due this fall… just with some sort of undefined compromise. (That could mean more aggressive alert dialog boxes or even a requirement that you set your Mac to run in a 32-bit compatibility mode complete with performance and feature penalties. Or something else. We just don’t know.)

Do the math: that means it will probably be at least 18 months before there’s a new release of macOS that absolutely refuses to run 32-bit apps at all, so there’s no need to panic. Deep breath. There’s time.

That said, if you are alerted by macOS 10.13.4 that an important app you use has failed the 64-bit test, it’s worth checking with the developer of that app to see if there’s a newer version or if there are plans to release an updated version in the future. If not, you may eventually be forced to find an alternative or keep a Mac (or emulator) around running an older version of macOS.

(Before you send a strongly worded message to that developer, be sure to visit the app’s website. You may find that the developer has already posted an update about its plans for 64-bit compatibility. Adding 64-bit compatibility can be a lot of extra work for developers, and since the feature isn’t yet required, they may be planning on implementing it later this year. Seeing this alert doesn’t mean an app’s developer is sleeping on the job.)

Architecture transitions take a long time. This transition is well underway, and at some point 32-bit apps will be a thing of the past, but there’s still a ways to go before that happens. Apple has, as yet, not made any firm announcements about when that might happen, though we might hear more of that in June at the company’s annual developer conference.

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