How to Tell if Your Mac is 32-bit or 64-bit

Your app will still work after the alert appears; the main objective of the alert is to encourage users to update the app to a current 64-bit version.

Apple hasn't confirmed exactly when 32-bit app support is being completely dropped from macOS. The alert is similar to the ones that appeared when Apple transitioned iOS from 32-bit to 64-bit. Apple announced that it is killing off support for legacy 32-bit apps in macOS at last year's Worldwide Developers Conference. The company's desire to banish 32-bit software and move everyone to modern, 64-bit versions is no secret and now it is starting the process of encouraging people to make the switch. "They say "[app name] is not optimized for Mac" and they only appear once so as not to be a pest, but it's a gentle nudge for users and developers alike that the future for Apple is very much going to be based on 64-bits. Like, the 64-bit architecture enables taking advantage of more memory than its 32-bit counterpart. If it says No, it's a 32-bit app and you should check with the developer to see if an update is available, if you think you want to continue using the app in the future.

Users on macOS High Sierra 10.13.4 will see a one-time warning when they open apps that run on 32-bit technology. The technologies that define today's Mac experience-such as Metal graphics acceleration-work only with 64-bit apps.

New apps that were to be submitted to the Mac App Store in January 2018 had to be of the 64-bit variety and developers would also have to upgrade all existing apps in the App Store to 64-bit by June 2018 if they wanted their apps to remain approved for listing. For this, one needs to go to the Apple menu and select This Mac, and then click the System Report button. Under "Software" in the sidebar, look for "Applications", then sort the list by "64-bit (Intel)". After switching to 64-bit FOR outdated programs will cease to work. There could be one on the developer's website, or in Apple's App Store.

For now, the iPhone maker is just giving out warnings, and it has given no specific dates when the OS will totally stop supporting the 32-bit apps. Still, users can already check which apps they're running on their Macs need to be updated before the transition happens.

"This application is not optimized for your Mac", says the warning.