One A9 is the flagship phone from HTC and the bootloader unlock and TWRP is already available for it. So now you are all ready to start with the advanced development. However, during this process, you may also brick your device as the development is at it’s initial stages. The RUU program has been developed in order to flash stock firmware on HTC devices and restore everything to stock with ease. There are three methods to flash the stock ROM. If you have the RUU zip file then you can directly flash it through the bootloader, either with fastboot commands or from within the bootloader itself. However, if you have the .exe file then you will need to connect your HTC device to PC with the latest drivers. For easy connectivity, HTC Sync is recommended.

If for any reason you have installed a custom ROM or have heavily modified your system on HTC One A9 device, then you can flash the stock firmware with these RUU files. Moreover, you may not receive OTA updates on a rooted device with a custom firmware. For the OTA updates, you need stock recovery. You can also unbrick your A9 device if you get into a bootloop or stuck on logo/boot animation.

These are signed and combined firmware files for various variants like the USA unlocked, At&T, Europe and more. Hit the download section for the latest firmware for your variant. Although other HTC devices need S-OFF for the combined RUU, some of the members have successfully flashed it with S-ON for the HTC One device.

To start with here is a tutorial that will help you successfully install stock firmware on HTC One A9. Follow the instructions carefully and verify the firmware and your device.

Warning: Going through this procedure may void warranty. This isn’t an official method to flash the firmware file. We, at DroidViews, won’t be liable for any damage to your device whatsoever. We won’t be held responsible if you brick your device. Reader’s discretion is advised.


  • RUU Files for HTC One A9 — Link 

Backup Apps and Data
This process wipes all of your data. Hence, a backup is highly recommended. Make sure you backup your system, data, etc. on your PC. It will be helpful in case anything goes wrong.


  • This guide is compatible with various HTC A9 devices. Verify your device or variant with.
  • Unlocked bootloader is required to install a custom recovery like TWRP on your device. For reference visit this page.
  • Set up ADB and Fastboot on your computer. You can download the full Android SDK from here, or get the quick ADB and fastboot installer from here. For Mac or Linux OS, click here. You may also like HTC fastboot tool for the A9 device.
  • Install HTC USB Drivers on your computer.
  • Open Settings> Developer options and enable USB Debugging on your device.
  • Go to Developer options and enable Allow oem unlock, if such an option is available.

Method 1: Restore HTC One A9 to Stock Firmware with Fastboot

  • Download the RUU zip file. You don’t need to extract the file. just transfer the file to your PC where you can easily locate it.
  • Make sure you have setup ADB and fastboot on your PC. Also, accept Always allow from this computer when you plug in the device for the first time to enable USB Debugging.
  • Now power off your device and unplug it from your PC.
  • Boot into the bootloader or fastboot mode. To do so, turn off your device and then press and hold  volume down + the power button simultaneously for a few seconds. When you see the bootloader screen, connect your device to the PC using a USB cable.(Choose fastboot if option is available) For an alternative method look at the end of method 1.
  • Navigate to the location where you have placed the RUU file. Rename the recovery file to a simple one, like htc_a9_ruu.img. While the folder with htc_a9_ruu.img file is open, hold the shift key on the keyboard and right-click on an empty space and select “Open command window here” option to launch a cmd window.
  • Now issue the following command in the command prompt to check your device connectivity
fastboot devices
  • Now flash the RUU. Issue the following command for that.
htc_fastboot flash zip <file name>.zip
  • Now the firmware will start installing.

Once you have installed TWRP, you are all set to install custom packages onto the device’s system. Alternatively, while on Linux or Mac OS, you can issue “./htc_fastboot flash zip <file name>.zip” command to flash the RUU zip file.

How to boot into bootloader or fastboot mode using ADB

You can also issue the following command through your cmd or terminal, while connected to the PC, in order to boot into the bootloader. First setup ADB and fastboot environment from requirements and then follow instructions till step 5. Once into the command prompt or terminal, issue the following command:

adb reboot bootloader

Method 2: Restore HTC One A9 to Stock Firmware with RUU.ZIP File

Here is an alternative method for installing the file.

  • First, rename the RUU zip file to “”, save it at the root of your external SDcard.
  • Reboot the phone in bootloader mode. Refer to the method one in order to boot into bootloader.
  • Now it will start scanning the SDcard and detect the file.
  • When asked, “Do you want to start update?”.
  • Use your volume Up/Down key to start or cancel the flash.
  • Wait for the process to complete and don’t turn off your phone during the flash.

Method 2: Restore HTC One A9 to Stock Firmware with RUU.EXE File

If you have the RUU.EXE file, then the above methods won’t work for you and the flash process will be comparatively easy. The zip files have been extracted from the files. To go through this process successfully, make sure you have the latest HTC drivers or the HTC Sync installed. Connect your phone to your computer and launch the RUU.EXE file. Follow instruction from the RUU program.

Once you successfully update your phone software, you can now enjoy your stock firmware.

For queries, comment down below. Like and share us on social platforms. If you need help with other devices, let us know.

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