An RUU is typically a Windows-executable (.exe) file that contains a complete system image, including the boot, recovery, and system partitions. When executed, it overwrites the current software on your device with official factory firmware.
Using the HTC RUU Flash Tool requires some technical expertise and caution. Here's a step-by-step guide on how to use the tool: Htc Ruu Flash Tool Download
A user attempted to flash an unofficial AOSP ROM on their HTC U11 (S-ON, US Unlocked). The ROM corrupted the system partition, leaving the device boot-looping at the HTC logo. Fastboot was accessible. An RUU is typically a Windows-executable (
The Android development community has preserved HTC RUUs. The safest sources include: including the boot