How does app know I have an account already with them when I formatted

[styleand]

There is this app that knows when I sign up for a new account that I have an account with them. When I use a different device and put it in the device they know, I am able to to use the trial. I formatted the device and they still know I have an account. Will rooting help and changing other stuff. I am not sure what they are reading to find out I have signed up before.

I am able to use a new device and put that information to the old device and works fine, but I would have find a new device all the time. What can I do to know what they are reading to bypass.

 

[B. Diddy]

Welcome to Android Central! Probably because in the Settings>Backup & Reset menu, you're saving app settings to your Google account, and when you reinstall the app, it's automatically restoring those settings if you have Automatically Restore also checked on.

 

[styleand]

No I didn't have any link account when I formatted. I created a new account and fully formatted it. I even tried it on a retail mode android. I got the an account from retail and then when I resetted the retail it erasers all previous information or anything saved. I then create a new account and downloaded the app and it knew that I was signed up.

Could it be that it's reading mac address, phone serial number or tablet serial number. If it is can a rooting my device get me a new mac address, serial number, etc.

 

[B. Diddy]

I might not be understanding correctly, but are you logging into this app with the same username as before? If so, then it's not surprising, since the company would have your app username and account information saved on their servers. Or are you creating a whole new username and account on the app?

Which app is it?