To help developers check if their software is ready for 64-bit, Apple added a new tool for developers in Xcode 9. With this tool, you can force macOS to run as “64-bit only” to see if your software is ready for a 64-bit only environment.
To try your apps in this test mode:
- Launch Terminal
- Execute the following command: sudo nvram boot-args=”-no32exec”
- Restart macOS
64-bit test mode prevents 32-bit processes from launching. Launching an app that depends on 32-bit software results in a notification that the application can’t be opened. Other types of software may fail silently, such as 32-bit versions of Dashboard and WebKit plugins, preference panes, and background processes. Disable the test mode once the software is updated to work in 64-bit.
To disable the test mode:
- Launch Terminal
- Execute the following command: sudo nvram boot-args=“”
- Restart the machine
Remember that macOS High Sierra 10.13 is the last version to run “32-bit software without compromises”. Although macOS Mojave 10.14 still runs 32-bit software, subsequent versions are expected to be 64-bit only.