With the release of the latest macOS developer beta, Apple will begin to alert users that they are using older, 32-bit apps, instead of the more modern 64-bit apps, the company told me today. The macOS beta will be released to developers on Wednesday.
At this point, the alert is more of a gentle reminder to users that their apps are out of date. You will receive an alert once per 32-bit app, so it won’t be an annoyance, but certainly something you should pay attention too.
Further alerts will happen when the next-generation macOS is released, most likely later this year.
Apple said they aren’t announcing a timeframe for cutting off support for 32-bit apps in macOS, but clearly that time is coming in the next year or so. This is a way for the company to start making people aware of the change, giving them plenty of time to make the necessary arrangements to update their apps.
While the alerts are only in the latest beta version of macOS, end users will start seeing them when version 10.13.4 is released to the general public. That will most likely happen in the next few weeks.
Developers were made aware of this change at WWDC last year, so none of this is new to them. If you see an alert, you should check to see if there is an updated version of that app.