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Hey @RolandsR, a warm welcome to the Community.
I just wanted to let you know that I have moved you post from the Charge 3 board to the Android app board, since I think that here you will be able to see more related topics about the Fitbit app.
Fitbit is compatible with more than 200 of the most popular Android, iOS and Windows mobile devices.
The full list of compatible devices with confirmed compatibility can be found here. If a device isn’t listed it doesn’t mean it won’t work with a Fitbit tracker or smartwatch. We routinely test new devices to ensure full compatibility with Fitbit devices and the Fitbit App, and are constantly working to confirm compatibility with new phone models.
A majority of Android phones running version 4.4 or higher will work with our products, however we cannot guarantee optimal performance on devices for which we have not tested and confirmed compatibility.
Let me know if you need anything else. 
Best Answer