Install Android 6.0.1 on GSM HTC One M9 using Slim6 Alpha Custom ROM

the Alpha builds of Slim ROM is now available for the HTC One M9. This custom ROM is based on the AOSP Android 6.0.1 releases and the Alpha builds of latest Slim6 Marshmallow custom ROMs. Here is how to install Android 6.0.1 using Slim6 Alpha Custom ROM on HTC One M9 (GSM) that brings tons of extra features designed by the SlimROMs team. Some of the highlighted features are in Slim6 Alpha builds Slim Launcher, DPI Changer, root access, Slim Doze, Ambient display options, proximity wake, proximity speaker, toggle (wake up the phone when its charging) etc. You can learn more about this ROM by visiting this Slim6 ROMs.

If you want to install Slim6 Alpha Android 6.0.1 Marshmallow custom firmware on your HTC One M9 then go ahead and follow the given guide. Keep in mind that this is a custom ROM which is not officially released by Samsung thus you’ll need to have the latest version of a custom recovery already installed on your phone.

Install Android 6.0.1 on GSM HTC One M9 using Slim6 Alpha Custom ROM 1

Proceed to install this ROM and follow the given instructions to install Android 6.0.1 Slim6 Alpha ROM on HTC One M9. All you need to have your device rooted and the latest version of a custom recovery like (ClockworkMod recovery / TWRP recovery) already installed on your HTC One M9 in order to flash the Slim6 Alpha custom ROM and Google Apps package.


This guide containing the Slim6 Alpha Android 6.0.1 Marshmallow custom ROM is working with the HTC One M9 (GSM Version) Do not try to install this ROM on any other device, or your device might get bricked.


AndroidBlog will not be held responsible for any kind of damage occurred to your HTC One M9 during or after the installation of Slim6 Alpha Custom Firmware. Proceed at your own risk.


  • Make sure that the battery level of your HTC One M9 is at least about 80% before proceeding to the installation guide.
  • Download and install proper USB Drivers for the S6 on PC.
  • It is highly recommended to take a proper back up of your important data and settings on the phone using a custom recovery such as CWM or TWRP. In case anything goes wrong then you’ll be able to restore your data.
  • Enable USB Debugging Mode on S6 from Settings > Developer Options.
  • The HTC One M9 should be rooted with the latest version of CWM or TWRP recovery installed that it supports the new Android 6.0.1-based ROM installations.

Required Files:

Steps to Install Slim6 Android 6.0.1 Marshmallow Custom ROM on HTC One M9 (GSM Version):

Here we have given a step-by-step guide on how to install Android 6.0.1 Marshmallow based Slim6 Alpha custom ROM on HTC One M9.

1:- First, download the Slim6 Alpha Android 6.0.1 custom ROM (Download and Google Apps package from the above links on the desktop of your PC. Do not extract these files.

2:- Now, connect your HTC One M9 to the PC using its USB data cable.

3:- Move the Slim6 Alpha firmware and Google Apps zipped files to the root folder of SD card on your phone.

4:- Now, disconnect the device from the PC and boot into Recovery Mode.

  • Navigate to access Menu -> Settings.
  • In Settings, tap on Battery and uncheck the Fastboot option.
  • Power OFF your HTC One M9 and wait for a while before proceeding to the rest of the steps.
  • Press and hold Volume Down button; while doing so press once Power key in order to power on your device (Do not release the Volume Down key though).
  • HTC One M9 will be rebooted into Bootloader Mode.
  • You can use fastboot mode from here.
  • Once in fastboot mode, use Volume Up and Volume Down buttons for scroll down and up and Power key to select.
  • Highlight the recovery option and select the same and wait for a few seconds, your device will be automatically rebooted into recovery mode.
  • In Recovery, go back to Android OS by selecting “reboot system now”.

5:- Go back the main Recovery menu and choose install zip from sdcard > choose zip from sdcard.

6:- Find the ROM file that you’ve already transferred to the root folder of your SD Card in Step No 3. Select the Slim6 Alpha ROM .zip file and proceed the installation process.

7:- Once the ROM is successfully installed on your HTC One M9, install Google Apps package by following the same procedure as given above.

8:- After the installation of Slim6 Alpha Android 6.0.1 Marshmallow custom ROM and Google Apps, select reboot system now to reboot the HTC One M9.

It will take about 5 minutes to boots up for the first time after installing ROM on your phone.

That’s All! You have successfully updated HTC One M9 to the latest Android 6.0.1 Marshmallow with Slim6 Alpha custom ROM.

If you need more help with this guide you can tell us in comments.

Aamir Jamal

An Android Geek and audiophile who love to read and write reviews/tutorials about gadgets and new tech stuff. He has written 1007 guides and other posts.

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