Based on official Android 6.0.1 Marshmallow, an unofficial CM13 custom ROM is now available for Samsung Galaxy S3. Bringing all the usual CyanogenMod features, you can now update Galaxy S3 T999 to Android 6 Marshmallow.

Prerequisites to update Galaxy S3 T999 to Android 6 CM13:

Backup any important datafrom your Samsung Galaxy S3 SGH-T999 as a complete wipe will be required during the flashing process.Enable USB debugging option on your device:Settings>DevelopmentOptions>USB debugging.Samsung Galaxy S3 T999 must berooted, unlocked and installed with a recovery tool likeTWRPorCWM.Your device must be charged to at least 60% of power.

Note:this tutorial is focused on T-Mobile Samsung Galaxy S3 SGH-T999; please do not try this guide on otherAndroid&Samsungdevices. The unofficial ROM is still in ALPHA phase, so please beware that some features might not function at their best.

How to update Galaxy S3 T999 toCM13 Android 6.0.1:

Required files: download CyanogenMod 13 Android 6.0.1custom firmware for Galaxy S3and save it on your computer. Do not extract the contents.

ConnectGalaxyS3 to your computer using a USB cable and copy the zip file to your phone’s SD card.Disconnect the USB cord andpower off yourGalaxy S3.Boot it intorecovery modebypressing and holdingVolume Up+Home+Powerbuttons together.Perform aNandroid backupof your current OS:Backup >backupand restoreon ClockworkMod recovery.Wipe data task: from the CWM recovery menu, selectwipe data / factory resetand confirm the process. Then go on towipe cache partitionandwipe dalvik cache.From recovery menu, selectinstall zip from sdcard,followed bychoose zip from sdcard.Locate the CM13 Android 6.0.1custom firmware and confirm the flashing process.Return back to main recovery menu and reboot your T-Mobile Samsung Galaxy S3 into the new custom ROM. First bootmay take a few longminutes.

How to restore:If you want to return to previous OS on your SGS3, boot intorecovery, selectbackup and restorethen restore yourprevious ROMby selecting it from the list.

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