Starting on April 12th, macOS users will begin receiving messages indicating that apps installed on their system are 32-bit, and will require an update. At our Worldwide Developers Conference in 2017, Apple informed developers that macOS High Sierra would be the last version of macOS to run 32-bit apps without compromise. The supportpage explains why Apple wants all Mac software to be 64-bit. Last summer, the company was users that 32-bit apps would be disabled in a post-High Sierra update.
Apple began the transition to 64-bit hardware and software technology for Mac over a decade ago and is working with developers to transition their apps to 64-bit. A one-time alert has been pushed out to those running macOS 10.13.4 which will trigger once users launch a 32-bit app.
The document also includes a new FAQ that addresses concerns like potential data loss and 32-bit app support on macOS High Sierra.
"All modern Macs include powerful 64-bit processors, and macOS runs advanced 64-bit apps, which can access dramatically more memory and enable faster system performance", Apple said in its statement.
The 32-bit phase-out on macOS follows the complete transition to 64-bit apps on the iPhone, though there Apple has more control due to the App Store. When you select an individual application, you will see a field titled "64-bit (Intel)". Then scroll down to Software and select Applications. "Yes" indicates 64-bit; "No" indicates 32-bit", the page reads. However, it is believed that the 32-bit apps won't work as well as they use to before. Apple usually unveils the next major versions of its operating systems at that event, so it makes sense that Apple could provide more details then. It will also support universal apps or apps that will work across Mac and iOS devices, according to MacRumors.
Apple likely won't completely disable 64-bit support for many months to come, so developers still have a while to update their apps. The bar on 32-bit iOS apps was one of the key reasons the number of iOS apps in the App Store fell past year. For the next four years after the A7 chip, the company encouraged developers to move to 64-bit. There could be one on the developer's website, or in Apple's App Store. Further, a user also gets the option to delete it or keep it, even though the app can't be used, notes CNET.