Mac: If you depend on any older software, you’ve probably seen a cryptic message today. It means you’re using a 32-bit app.

“This application is not optimized for your Mac,” says the warning. “This app needs to be updated by its developer to improve compatibility.”

The message doesn’t mention 32 bits, but that’s what this is about. Apple plans to eventually stop supporting 32 bit macOS applications entirely, and this warning is just one step along that path.

RELATED: How to Check Your Mac for 32-Bit Applications That Will Stop Working After High Sierra

The current version of macOS, High Sierra, will be the last version of to run 32-bit apps “without compromise,” according to Apple. Here’s Jason Snell, writing for Six Colors:

While Apple hasn’t detailed exactly what “without compromise” means, it’s my understanding that 32-bit apps will run on the successor to High Sierra due this fall… just with some sort of undefined compromise. (That could mean more aggressive alert dialog boxes or even a requirement that you set your Mac to run in a 32-bit compatibility mode complete with performance and feature penalties. Or something else. We just don’t know.)

Whatever this all means, it’s likely your 32-bit applications will keep working on the macOS version coming this autumn, but possibly not on the release after that in the autumn of 2019. Apple’s potential transition away from Intel might be related, but that’s just speculation.

Whatever the case turns out to be it’s a good idea to know how many apps you depend are 32-bit. We explained how to check your Mac for 32-bit applications last year. We suggest you check now and, if possible, find out if developers plan on releasing 64-bit versions. If not, you’ll eventually need to replace that software. Guess I’ll have to find a new version of Tetris.