FolderSync is as the name suggest a folder syncing application. It is not a traditional backup application, although it can be used to backup files if you configure it correctly. Its primary purpose is to sync folders between your devices and remote cloud provider or a server.
Using FolderSync to backup files
As mentioned FolderSync can be used to backup files, but it will not retain files if you configure a folderPair to also sync deletion of files. In that case any deletions will be synced as well, and files will not be retained. Sync deletions are disabled by default, so unless you enable it, FolderSync will never delete files.
FolderSync can be installed from Google Play or by installing purchased APK manually.
FolderSync requires Android 6.0 or newer.
How to install APK on Android
See this guide for help with installing an APK file on Android.
There are two FolderSync apps available on Google Play:
- FolderSync Pro - paid app, must be purchased for download
- FolderSync - free app, has in-app purchase named "Premium" that unlocks it to remove ads and be identical in function to "FolderSync Pro"
Upgrading the free app using in-app purchase does not enable download of the Pro version. Likewise, the purchase of the Pro version doesn't unlock premium in the free version. Technically they are different apps on Google Play and your purchase is tied to the app that was purchased either as a paid app or in-app purchase.
Re-installing on another device etc.
In general your purchase will be tied to your Google account, so remember to use the same account when reinstalling or installing on a new device. As for family sharing in countries that support it, this will probably only work for the "FolderSync Pro" version.
Problems downloading or unlocking premium upgrade
If you can not download the pro app or the free version doesn't remove ads when premium upgrade has been purchased, and when using the Google account previously used for purchase, this issue can sometimes be solved by force closing Google Play or restarting the device. If that doesn't work I suggest contacting Google Play support here.