The HTC One bootloader loads the system software on your phone and determines which applications will run during startup. When you unlock the Bootloader on your HTC One phone, you will now have the ability to customize the software on your phone. You can now install custom ROMs and a bunch more and unleash the power of the HTC One.

Checklist before getting started:

• Ensure that you have your HTC One fully charged
• You will need the HTC Sync Manager software which you can download here
• You will also need Android SDK installed for using ADB which you can download here
• Take a backup of your phone including any pictures, contacts etc. since this process could delete everything on your phone

Now that you have everything ready, follow the simple 6 step checklist to unlock the HTC One Bootloader

Step1: Register & Begin Unlock process

• Visit HTC’s website htcdev.com/bootloader. You will be asked to register on HTC website before logging in.
• You will be asked to verify your email. Once verified, log in to the HTC Dev account
• In the Supported Devices column on the right, from the options, scroll down all the way to the bottom and select All Other Supported Options
• Click on the Begin Unlock Bootloader option and accept the dialoag boxes presented

Step 2: HTC One in Bootloader Mode

• The next step is to put the device in Bootloader mode. 
• Disconnect the phone from the PC,  power it down completely
• Now, press and hold the Volume Down button and the Power button to begin the Bootloader mode process
• Once in the bootloader mode, use the Volume button to choose the Fastboot option. Now press the Power button to select
• Connect your phone to the computer using a USB cable

Step 3: ADB and Fastboot files on your PC

• If you followed the pre-checklist, you would have installed the Android SDK
• Run the SDK Manager.exe (found in \android-sdk-windows\)
• Create a new folder (example C:\Android) where you will be placing 3 files in the folder. They are
• adb.exe (look in \android-sdk-windows\platform-tools)
• adbWinApi.dll (look in \android-sdk-windows\platform-tools)
• fastboot.exe (look in \android-sdk-windows\tools)

Step 4: Get Identifier Token

• Now, open a command prompt (start>run>type cmd). Go to C:\Android folder (type cd c:\Android) , or the folder you created above
• Type fastboot oem get_identifier_token
• You will now see a long text block. You need to copy the block betwee the lines <<<< Identifier Token Start >>>> and end with the line <<<<< Identifier Token End >>>>

Step 5: Send the Token to HTC and receive unlock code

• Scroll down to the bottom of this page http://www.htcdev.com/bootloader/unlock-instructions/page-3
  
• Under My Device Identifier Token, enter the block of text you copied in the step earlier and hit submit
• You will then recieve your unlock code binary file called Unlock_code.bin

Step 6: Unlock your HTC One Bootloader

• Download the above file and place in your fastboot folder
• At the command prompt, type fastboot flash unlocktoken Unlock_code.bin
• When prompted, use the volume button to select and hit the Power button to confirm
• The device will now restart and you now have a unlocked HTC One!! Congratulatiosn