allow website to track users mobile apps

allow website to track users mobile apps if they install the specific app or not

let me know if some know about this

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Our Website - R7rewards.cm
is based on paid task based website. where user can complete tasks and earn money
and we want our website can track the specific app . user download the app or not.

example- task - download this app and earn 5 rs

so we need to track the users activity when user download the app successfully then our system auto detect the user get paid the amount in his wallet