CyanogenMod-based CM12.1 series custom ROM, developed by varun.chitre15,  a senior XDA Developer Forum member, has been released to HTC's 2015 flagship smartphone One (M9).

The new CM12.1 firmware is based on HTC's Android 5.x.x Lollipop and is a beta version, so there are some glitches. They is no report of any serious bug that may affect overall performance of the device as such but only benign in nature.

Some of the features that need to be fixed include:

  • USB OTG
  • Camera
  • FM radio

Prerequisites (Things to remember before installing the CyanogenMod CM12 Nightly):

  1. The new CyanogenMod Android 5.1.1 Lollipop CM12.1 custom firmware has to be installed on the HTC One M9 (Global/AT&T/T-Mobile versions) models only ; if tried on other devices, it might get bricked [To check your device model: Go to Settings >> About phone >> model number]

[Note: CM12.1 ROM for Sprint and Verizon models are on way]

  1. Make sure the device is rooted before going forward for custom ROM installation
  2. Installation of custom ROM requires clearing of memory in the smartphone, so make sure to back all the data by installing Clockwork Mod (CWM) Recovery/ TWRP in the smartphone.
  3. Make sure to install USB drivers on the PC, or else the smartphone (HTC One M9) will not be recognized by the computer.
  4. Make sure your device has more than 80% battery, or else there is a chance of the smartphone getting temporarily bricked if the installation process is interrupted midway.

[Disclaimer: This procedure is very technical and should be performed by a person with sound knowledge of rooting (or manual software installation) Android devices. If the step-by-step installation process is not followed properly, there are chances of the smartphone getting bricked or being permanently irreparable. International Business Times, India Edition cannot be held responsible for any damage or claims from readers if the procedure does not yield the required results or if the smartphone is bricked. Hence, users are advised to proceed with caution.]

Tutorial: Step-by-step Installation Guide for c CyanogenMod [unofficial] Android 5.1.1 Lollipop CM12.1 Custom ROM on HTC One M9 -Global/AT&T/T-Mobile versions:

Step 1: Download CyanogenMod [unofficial] Android 5.1.1 Lollipop CM12.1 custom ROM (HERE) and Google Apps (HERE) in to your PC.

Step 2: Connect HTC One M9 to PC via USB cord.

[Note: Before plugging the phone to the computer, be sure that you have installed USB driver software, if not, click HERE to download the firmware]

Step 3: Place Android 5.1.1 Lollipop zip file and Google Apps files into the phone's SD card memory. [Note: Users are advised to paste the .zip file in SD card root, not in any other folder.]

[Note: Before installing the custom software, be sure that the device must have been rooted and has installed ClockworkMod Recovery tool.]

Step 4: Place boot.img file in to the android-sdk-windowsplatform-tools directory

Step 5: Turn off the device and disconnect from the PC.

Step 6: Perform the regular Bootloader mode sortie, by press holding 'Volume (Down)' and 'Power' buttons.

Step 7: After entering the Bootloader mode (on the phone), go to android-sdk-windowsplatform-tools directory (on the PC) and open Command prompt, then type in: 'fastboot flash boot boot.img' and press enter.

(To enter Command prompt: Shift + right-click >> open Command Prompt)

Step 8: Type - 'fastboot reboot' and press enter. Then, follow instructions displayed on the screen. Select BOOTLOADER option to enter Recovery Mode.

Step 9: After entering the Recovery mode, clear the phone memory, by choosing 'wipe data/factory reset' [Note: use Volume keys to navigate and power button to select options, while operating under Recovery Mode]

Step 10: Clear the cache memory by selecting 'wipe cache partition'.

Step 11: Go back to ClockworkMod recovery, and select 'advanced' and tap 'wipe dalvik cache' [Note: This step is optional, but many recommend this procedure so that user will not face boot loops or any other errors in the middle of custom ROM installation]

Step 12: Come back to main recovery screen and then tap 'install zip from SD card'

Step 13: Tap 'choose zip from sdcard' and go to Android 5.1.1 Lollipop ROM .zip file in SD card and enter the installation process. Repeat the same procedure for Google Apps [Note: use Volume keys to navigate and power button to select options]

Step 14: Once done with the installation process, navigate to '+++++Go Back+++++' and re-start the device by opting 'reboot system now' seen in the recovery menu.

Now your device (HTC One M9) will take a few minutes (only for the first time) to complete the booting process.

Head to Settings >> select 'About phone' to confirm the installation of CyanogenMod [unofficial] Android 5.1.1 Lollipop CM12.1 custom ROM.

[Credits: XDA Developer Forum, varun.chitre15, Rashed97, Flinny]