The Android 5.1 update is now available for download and manual installation on HTC One Max, thanks to Cyanogenmod 12.1 custom ROM, also called CM12.1. HTC is yet to release the Android 5.0 update, hence you cannot expect the official Android 5.1 update for One Max to arrive anytime soon. CM12.1 packs in cool features of its own to the mix along with Android 5.1, and this really makes for a good reason to install it if you wanna check out the 5.1 update live, and can’t wait for HTC’s OTA.

Please note that because this is not official update from HTC, in fact not even CM team’s own build, you may have to face several bugs with this 5.1 update. Sure, you’ll get to play with 5.1 on beautiful stock Lollipop UI — something which official HTC update won’t have — and try out new features outright, but sometimes, things could force close on this build. That’s not to say, it’s too unstable, but be sure to try it out fully before considering this Android 5.1 update as your daily driver.

Speaking of the Cyanogenmod ROM, well, it was one of the first custom ROM on Android, and still the most popular one. The CM team is now a company and even comes pre-installed on phones, like YU Yureka and OnePlus One.

Btw, if you or any of your friends has any of the devices mentioned below, know that Android 5.1 update is also available on these:

Note: Keep in mind that this is not an official HTC Android 5.1 update firmware, hence you may come face to face with nagging bugs many a times.

Bugs
  • Contacts app force closes when someone’s icon is clicked
  • If data doesn’t work, restart the device for once
  • More to be added later when found
Downloads

Grab the ROM file in .zip format from the source development page here, where you could also keep a tab on current issues with the ROM and fixes, if any, available. Also download the Gapps from the same page.

Supported devices
  • HTC One Max international model
  • Don’t try on carrier specific models of HTC One Max, like Verizon, Sprint, AT&T, etc., if any
Instructions

Warning: Warranty may be void of your device if you follow the procedures given on this page. You only are responsible for your device. We won’t be liable if any damage occurs to your device and/or its components.

Important Note: Backup important files stored on your device before proceeding with the steps below, so that in case something goes wrong you’ll have backup of all your important files.

  1. Transfer the ROM file package file to your device’s internal storage and remember the location where you save it.
  2. You need TWRP recovery for this. Get it from here. There’s good instructions set there, too. For more help, Google is your friend.
  3. Boot into Recovery mode.
  4. Once in TWRP recovery, take a backup of your current ROM. On TWRP, select Backup, then do a “Swipe to Back Up” on the bottom of the screen.
  5. Once the backup is finished, select Wipe, then do a “Swipe to Factory Reset” on the bottom of the screen.
  6. Go back to the main menu of TWRP recovery and select Install.
  7. Navigate to the file where you saved your ROM’s zip file, select it and “Swipe to Confirm Flash” on the bottom of the screen. Now wait until the flashing process finishes.
  8. Go to back to recovery’s Main menu, select Reboot » select System.

Your device will now reboot with Android 5.1 update, thanks to CM12.1 custom ROM.

In case you need any help over this, let us know. And, you can thank Flyhalf205 for this.