How to Update LG G4 to Marshmallow Android 6.0 update with stock ROM 20A

We earlier shared the LG G4 Marshmallow update’s KDZ file with you, which comes with software version H81520A. Here you will find the TWRP recovery flashable ZIP file, which was way easier to install using TWRP recovery, and are way more helpful when we’re finding trouble flashing KDZ files.

Below you will find all required links to help you install TWRP recovery, for which you will have to unlock your LG G4’s bootloader first, using LG’s own tool.

Which is why this method is only useful to you if your G4 is bootloader unlock-able from LG. At the moment, only international G4 sets are allowed by LG to be unlocked, so this is essentially Marshmallow update for those devices only.

Info: The TWRP flashable Marshmallow update we’ve here is 100% stock, and unrooted. For root, see here. Simply flashing the SuperSU file won’t do the trick. If you do that, you will soft brick your device, and will have to flash the files here again to recover it.


Marshmallow update (20A) files:

  • System  — Link | File: (1.33 GB)
  • Modem — Link | File: (39.31 MB)
  • Boot — Link | File: (13.08 MB)
  • Bootloader — Link | File: (35.43 MB)

Supported devices

  • LG G4, model no. H815
  • Don’t try this on any other device than the one having codename specified above.

BTW, we also have Marshmallow update for T-Mobile G4 here.

Use the Droid Info app, to determine the model no. of your LG G4. If it is exactly the one specified above, then it should be compatible with the 6.0 custom ROM we have here.


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.


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.

How to Install

Required: You will need to have TWRP recovery installed on your device to be able to install H81520A stock ROM. Check out our page on LG G4 TWRP recovery for this.

Step 1. Download the Marshmallow ROM files from above.

Step 2. Connect your device to PC and transfer all four files (system, modem, boot and bootloader) file to it. Disconnect the device then. Remember the location of the files.

Step 3. Boot your LG G4 into recovery mode. If you are rooted, you can use Quick Boot app from play store.

You will enter recovery mode soon, and should see TWRP recovery. If you see an Android with an exclamation mark, then you need to install TWRP recovery for this (linked above).

Step 4. [Optional] Once in TWRP, create a backup of your device. Tap on Backup, and then select all the partitions for back. Now do the swipe action at bottom to start creating a backup for emergency cases. This backup is really a lifesaver!

Step 5. Do a Factory Reset. On TWRP’s main screen, tap on Wipe, then advanced wipe, and now make sure you have selected these partitions: dalvik cache, data, system and cache. Then do the Swipe action at bottom to confirm it.

Step 6. Now, install the ROM file. On TWRP’s homescreen, tap on Install, and then locate the system file and tap on it.

Then tap on ‘Add more zips’ button and select the modem file. Then also add the boot and bootloader files this way.

With all four zip files added, do the Swipe action at bottom to begin flashing the them all one after another.

Step 7. When it’s done, tap on Reboot system button to restart the device.

That’s it.

The first boot might take some time, so be patient with this. Give it 5 to 30 mins or so. When the screen comes on, it’s better to let the device rest for 5 minutes so that new code settles dows quite alright. Then pick up your device and enjoy your Marshmallow.

LG G4 Marshmallow Root

Well, the root access is now available for Marshmallow on LG G4.

You basically have to flash a custom kernel that supports root because LG’s stock kernel doesn’t. Normally you have to flash SuperSU after installing custom kernel, but because the kernel we have comes with root injected already, there is no need to flash SuperSU. Find it at the link below.

→ How to Root LG G4 on Marshmallow update

Need help?

Let us know if you need any help with this via comments below.

Via autoprime

Posted by
Kapil Malani

A die-hard Liverpool FC fan, Kapil is a big fan of Batman, Android and street Cricket. In that order, probably. Email: [email protected]

1 Comment

  1. I’d suggest flashing all 4 zips. Bootloader first.. then order after that does not matter.

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