Uninstall trackers are now available for Android and iOS apps.

The tools essentially allow developers to identify if you’ve removed their app from your device.

This could open the door for targeted ads, prompting users to reinstall an app.

Mobile apps are already able to gather a ton of data about users, but you could previously uninstall them for some (supposed) peace of mind. Now, it seems that developers are able to track you even after removing the offending app, allowing them to potentially annoy you with prompts to reinstall it.

Adjust, AppsFlyer, CleverTap, MoEngage and Localytics are just a few of the companies offering uninstall trackers to Android and iOS developers, according to Bloomberg. Their customers include Spotify Technology, T-Mobile, Yelp, and Bloomberg‘s parent company.

The tool does have some potential uses, such as gauging reactions to an app update (more uninstalls equal a terrible update). But it doesn’t merely let developers know how many people have uninstalled an app…

How does it work?

The publication notes that uninstall tracking takes advantage of silent push notifications in Android and iOS. Silent push notifications are usually used for tasks where the device owner shouldn’t be alerted, such as refreshing your inbox.

An app is deemed uninstalled if it doesn’t send a ping back to the developer. The uninstall tracker is then able to tie the “uninstalled” status to your mobile advertising ID, effectively identifying users and opening the door for annoying ads.

Editor's Pick The best Android smartphones with the best battery life We've seen more than a few studies that confirm smartphone users care the most about one thing: battery life. However, figuring out the best Android phones with the best battery life can be quite the …

We already see pesky notifications for some mobile games, calling on users to launch the title when you haven’t played it in a while. But imagine if you got those ads when you uninstalled the game in question?

Alex Austin, CEO of software company Branch Metrics, told Bloomberg that uninstall trackers violate Apple and Google’s policies (although they haven’t cracked down yet). Austin added that his company decided against building an uninstall tracker.

“It’s just generally sketchy to track people around the internet after they’ve opted out of using your product,” Austin said, according to Bloomberg.

Would you download an app if you knew it would send ads to you after uninstalling? Give us your thoughts in the comments!

NEXT: Here’s what the Google Pixel 3’s Night Sight camera can do