Apple will start warning Mac users this week that 32-bit app support in macOS is coming to an end. Ars Technica notes that Mac users running macOS 10.13.4 will receive a one-time alert tomorrow that will trigger once a 32-bit app is opened. The alert simply reveals that an app is “not optimized” for a Mac, but the app will continue working for now.

Apple has not yet revealed exactly when it will fully cease supporting 32-bit apps on macOS, but the company has previously warned developers about the change and noted that High Sierra would be the last version to support 32-bit apps “without compromise.” Apple has been making the transition to 64-bit hardware and software for more than 10 years, and the company already stopped accepting 32-bit apps into the Mac App Store.