The Fast file transfers feature on HTC 10 lets you transfer files with high speed using a USB 3.1 cable. If the option is inactive for you, then do as follows to enable fast file transfers on HTC 10:
1. Connect your HTC 10 to the other device using a USB 3.1 cable. Make sure the PC you are connecting your device to, must support USB 3.1.
2. Open the Settings app
3. Under the Wireless & Networks settings, hit the More option
4. Tap to open the USB Connection settings
5. Touch the USB Connection option and make sure the connection type is set to Charging. (If you select the File Transfers option, the Fast File Transfers option will be inactive and the gray icon cannot be toggled on)
6. Now, toggle on the Fast file Transfers option.
7. Hit OK and you are good to go. Let's transfer files with higher speed