As of September 2018, support for 32-bit applications on Mac systems is slowly but surely waning. While most applications will still run properly with macOS High Sierra 10.13.4 and onward, applications that have not been updated to use 64-bit processes will produce a one-time alert when opened. This gives users advance notice that they are running 32-bit software, which may not be compatible with macOS in the future.
You can, of course, continue using your 32-bit applications with your Mac today. Using 32-bit software has no nefarious effect on your data, your computer or your external devices.
If you want to check whether an application is 32 or 64-bit you can do so as follows:
- From the Apple menu, choose About This Mac.
- Click the System Report button.
- Scroll down to Software in the sidebar.
- Select Applications.
- When you select an individual application, you will see a field titled 64-bit (Intel).
Yes indicates 64-bit; No indicates 32-bit.
- If you're using macOS Mojave, select Legacy Software in the sidebar to see all applications that have not been updated to use 64-bit processes.