When Apple introduced macOS High Sierra last year, it shared its plans to phase out 32-bit apps on Macs and yesterday, the company officially announced during its WWDC keynote that macOS 10.14 Mojave will be the last version of Apple’s desktop operating system to support legacy 32-bit apps (via MacRumors).
On macOS High Sierra 10.13.4, when you open a 32-bit app, a warning is displayed about its future incompatibility with the macOS. A similar dialogue is also displayed when opening 32-bit apps in macOS 10.14 Mojave beta 1, except this time, the warning clearly says “This app will not work with future versions of macOS”.
The above dialogue is displayed when opening the 32-bit Firefox app in macOS Mojave.
“Currently, the warning is only shown one time for each app. That could well change in subsequent betas of macOS Mojave, however, since Apple previously said it would include “aggressive” warnings about 32-bit apps in the next version of macOS after High Sierra before they are phased out entirely.”
Looks like users will need to find replacements for older 32-bit apps that aren’t likely to be updated to 64-bit on future versions of macOS.