Developers need to make sure the apps and updates they submit to Apple’s Mac App Store are 64-bit starting on January 31st, 2018. Apps that are currently 32-bit must be updated with 64-bit support by June 2018.
In a note to developers Apple said,
Starting January 31, new apps submitted to the Mac App Store must support 64-bit, and Mac app updates and existing apps must support 64-bit starting June 2018. If you distribute your apps outside the Mac App Store, we highly recommend distributing 64-bit binaries to make sure your users can continue to run your apps on future versions of macOS. Build and submit your apps using Xcode 9.2.
That doesn’t preclude developers from offering 32-bit apps outside of the Mac App Store. The 32-bit apps users have already installed will continue to work, too.
Apple’s warning to developers is a good reminder that the end of support for 32-bit apps in macOS is looming on the horizon. Apple plans to drop support for 32-bit apps in 2019, so you still have time to find alternatives for the apps you use that haven’t been updated in a long time—or to decide if sticking with older versions of macOS is the right move for you.
You can find out which apps on your Mac are still 32-bit by checking the built-in System Report. Check out TMO’s tip explaining how.