Also the device should have a CWM or TWRP Recovery tool installed on it.
Now, enable the USB Debugging Mode from the device’s Developer Options menu.
This option will allow transferring different files between device and the PC.
Note that, if the Developer Options menu isn’t displayed in Settings, then you need to follow the next path: About Phone, and from there scroll down and tap seven times on the ‘Build Number’ section.
You will need to take two extra preparation steps: the NANDROID ROM backup and the Factory Reset ones. Do not try to skip either one of these steps.
In case you want to save different data or applications, SMS text messages or any other type of data then you can use a suitable backup and restore tool such as Helium application for Android.
Now, sync the Contact and People details with your Gmail Account.
This step by step guide should be used by advanced users.
Now, check the device’s battery charge level and be sure that the device has more than 65 % power left in its battery, so that it won’t turn off in the middle of the installation process.
We, Android Source Team cannot be held liable or responsible for any data lost or bricking the HTC One M8 device in case you’ll lose any of your important data.
Check and follow all steps from this guide and do not skip any of them.
How to install the new CM 11 Android 4.4.3 Nightly for HTC One M8 device:
Firstly, download the CM 11 Nightly zip file from here, make sure that you will download the latest version build possible.
Secondly, download the new Gapps for Android 4.4 x ROM from the link.
Now, connect the HTC One M8 device to the PC and copy both zip files to its internal storage, after the transfer has been successfully done you can disconnect the device from the PC.
If you want to download the flashing files directly on your device, then you need skip this step.
Turn off the device completely.
Now, boot the device into Recovery Mode. (Both CWM and TWRP custom images are supported by this step by step guide).
Next, get a Nandroid Backup for the actual installed ROM:
For CWM, select the “Backup and Restore” option, then name the file and confirm the process.
For TWRP select the “Backup”, name the file and then confirm the process.
Now, apply a Factory Reset action : For CWM: select the ‘wipe data/ factory reset’ and confirm the removal of user data, if you have a TWRP custom ROM press the Wipe and then simply swipe to perform the factory reset action.
Now, flash the CM11 Android 4.4.3 custom ROM on your HTC One M8 device.
For CWM, select the “install zip from SDcard” and then “choose zip from sdcard”. Browse the custom ROM file and the flash it.
For TWRP, press Install button from the menu, browse your device’s internal storage and get the installation file, confirm its installation.
When the new custom ROM is successfully installed you can continue to install the Gapps zip by using the same procedure as above.
After you manage to flash all files you need to reboot the device into normal mode.
Use your Google information and take all control over your device once again.
Congratulation, these were all instructions that you need to perfume in order to successfully update your HTC One M8 device to Android 4.4.3 CM 11 Nightly custom ROM.
For any other supplementary questions please use our comments section from below.