When iOS 11 is released later this year, nearly 200,000 apps will no longer work on updated phones, according to Sensor Tower.

Developers working in a beta version of iOS 10.3 found popups on old apps warning that apps designed for 32-bit processors would not work on future versions of iOS, usually those notifications just warned that the app could slow down the phone.

Read: iOS 11: Rumors On What Apple's Next Mobile OS Will Have On Its Release Date

The new update will be incompatible with 32-bit apps, the developers speculate. Sensor Tower analyzed App Intelligence data and concluded that roughly 187,000 apps that have either ranked as top free, paid or grossing charts out of 2.4 million wouldn’t work if 32-bit apps were not longer supported.

How do you know which apps won’t work on iOS 11?

The first iPhone that operated on a 64-bit processor was the iPhone 5c running on iOS 7. For any app to run on the iPhone 5c or newer, it had to be compatible with a 64-bit processor.

In the App Store, when you look at an app’s details, there is a section called “compatibility.” This section will say which version of iOS is necessary. So if it is compatible with iOS 7 or newer, you know it’s compatible with a 64-bit processor.

Apple stopped accepting new apps that didn’t support 64-bit processors in Feb. 2015, and existing apps had until June 2015 to update. Additionally, Apple started purging the App Store of old apps in October. It’s unlikely you would be trying to download any 32-bit apps, but were you to look at any old apps that were in your downloads, you may be able to find a 32-bit app there. When you attempted to download that app, you would get a notice saying the app may slow down your device and it needs to be updated, and that’s up to the developer.