The Fastboot feature on the HTC One M8 is used to enable the ability to flash partitions to the phone. It’s the same type of feature as “Recovery Mode” in that it allows you to load a ROM or image files that provide different “flavors” of Android such as LineageOS to your phone instead of the standard one included with the device.
You can enable or disable the Fastboot feature on the HTC One M8 by using these steps:
- From the Home screen, select the “Apps” button.
- In the “Device” area, choose “Power“
- In the “Fast Boot” section, check the “Fast boot” option to turn it on. Uncheck it to turn it off.
A utility is available for Windows and Mac that allows you to connect the HTC One M8 or other Android device to your PC and flash it with a desired ROM or image file. It is included with the Android SDK. If you don’t want to download and install the entire SDK, you can use the ADB, Fastboot, and Drivers provided over at XDA-Developers.