Originally written by Monojit Dutta, updated by Dibyajyoti Kabi. First published July 10, 2017. Updated October 24, 2026.
To flash LG stock firmware, you need the KDZ file for your exact model, the LG USB driver and LG Flash Tool on a Windows PC. Put the phone in Download Mode, load the KDZ in the tool, pick CSE Flash and click Start. It wipes the phone and puts it back on clean stock software.
This post used to be a quick guide from 2017, when LG was still making phones. LG has since left the phone business, so I’ve updated it with what still works, what to watch out for, and the full flashing steps for LG phones that are still in use.
Key points
- A KDZ file is LG’s full stock firmware package. Flashing it fixes most bootloops and soft bricks.
- Use the KDZ for your exact model number and carrier. A wrong file can hard brick the phone.
- CSE Flash wipes everything on the phone, so back up first.
- LG closed its phone business on July 31, 2021, so no new firmware is coming.
- Never flash a KDZ older than the one on your phone if your model has anti-rollback protection.
Is LG still making phones?
No. LG announced on April 5, 2021 that it would close its mobile phone business worldwide, and it finished the wind-down by July 31, 2021. LG said it would keep offering service support and software updates for a period after that, but current LG phones won’t see new major Android versions.
You can read the details in LG’s own press release. For you, it means the firmware already out there is the last firmware your phone will get. Flashing it is still the best way to fix a phone that won’t boot.
What do I need before I flash LG firmware?
You need a Windows PC, the original or a good data USB cable, the LG USB driver, LG Flash Tool and the KDZ file for your exact model. Charge the phone to at least 60 percent and turn off your antivirus while the tool runs, since some antivirus apps block it.
Here’s the checklist.
- Back up your photos, contacts and app data. My guide on backing up Android without root covers it.
- If you use a custom recovery, make a Nandroid backup too.
- Charge the phone to at least 60 percent.
- Find your model number in Settings > About phone, or on the label under the battery or on the box. It looks like LM-G900UM or LM-V600TM.
- Install the LG USB driver on your PC. My page with USB drivers for every Android brand helps here.
- Turn on USB debugging if the phone still boots. My guide on enabling Developer options and USB debugging shows how.
Where do I get the KDZ file for my LG phone?
Get it only from LG’s official support site for your country, or through LG Bridge or LG Mobile Support Tool if your model still shows there. Match the full model number and the carrier code exactly. A KDZ for a different variant, even one letter off, can leave the phone unable to boot.
I won’t link third-party firmware mirrors here. Many of them host old or modified files, and some bundle adware with the download. If you can’t find your firmware on LG’s site, ask your carrier or an LG service center first.
How do I put an LG phone in Download Mode?
Turn the phone off. Hold Volume Up and Volume Down together, then plug the USB cable into the phone while it’s connected to the PC. Keep holding until you see Firmware Update on the screen. On some older models, holding only Volume Up while you plug in the cable works instead.
If the phone boots normally, unplug it, turn it off again and try the other key combination. Pull the battery on older models with a removable one if the phone won’t power off.
How do I flash LG stock firmware with LG Flash Tool?
Open LG Flash Tool, pick the KDZ file, choose CSE Flash and click Start. Pick your region and language, check Clear Phone Software Registry and click OK. The flash takes 5 to 10 minutes, and the phone reboots on its own when it’s done.
Here are the full steps.
- Install the LG USB driver and restart your PC.
- Install LG Flash Tool. If it won’t open, install the Microsoft Visual C++ Redistributable from Microsoft and try again.
- Copy the KDZ file for your model to a folder on your PC.
- Put the phone in Download Mode and connect it to the PC.
- Open LG Flash Tool.
- Set Select Type to CDMA. It works for GSM phones too.
- Click the folder icon next to Select KDZ file and pick your KDZ.
- Click CSE Flash. This wipes the phone.
- Click Start.
- Pick your region and language, check Clear Phone Software Registry and click OK.
- Wait until the tool shows 100 percent and the phone reboots.
Don’t unplug the cable or close the tool during the flash. The first boot can take 10 minutes, so give it time before you assume something went wrong.
Should I pick CSE Flash or Normal Flash?
Pick CSE Flash when the phone is stuck in a bootloop or soft bricked, because it wipes everything and gives you a clean start. Normal Flash tries to keep your data, but it often fails when the software is badly broken, and you may need CSE Flash anyway.
| Option | Wipes data? | Best for |
|---|---|---|
| CSE Flash | Yes | Bootloops, soft bricks, going back to stock |
| Normal Flash | Tries not to | Reinstalling the same firmware on a working phone |
What is anti-rollback on LG phones?
Some later LG phones block firmware that’s older than the version already on the phone. If you flash an older KDZ on one of those models, the phone can refuse to boot or hard brick. Always flash the same version you have or a newer one, unless you’ve confirmed your model allows downgrades.
Check your current software version in Settings > About phone > Software info before you pick a file. If you can’t boot to check, use the latest KDZ for your model.
Why does LG Flash Tool not detect my phone?
Most of the time the LG USB driver isn’t installed, the cable only charges, or the phone isn’t in Download Mode. Reinstall the driver, try a different cable and USB port, and check Device Manager for an LGE Mobile entry under Ports. Then restart the tool with the phone already connected.
- Plug the cable straight into the PC, not a hub.
- Open Device Manager and look under Ports (COM and LPT) for an LG entry.
- If you see a yellow warning icon, reinstall the LG USB driver and restart the PC.
- Close LG Bridge or any other phone app before you open the flash tool.
FAQ
Does flashing a KDZ unlock or relock the bootloader?
No. Flashing stock firmware with LG Flash Tool doesn’t change the bootloader lock state. It replaces the software, removes root and replaces a custom recovery with LG’s stock one.
Will flashing stock firmware remove root?
Yes. A CSE Flash replaces the system and boot images with LG’s stock files, so root, Magisk and TWRP are all gone after the flash.
Can I flash LG firmware on a Mac?
Not with LG Flash Tool. It only runs on Windows. Use a Windows PC, or a Windows virtual machine with USB passthrough if you know how to set that up.
Does this work for Samsung or OnePlus phones?
No. Each brand uses its own tool. For a Galaxy phone, see my guide on flashing Samsung firmware with Odin. For OnePlus, see my guide on flashing stock OnePlus firmware.
Related guides
- How to flash stock OnePlus firmware
- How to flash stock Samsung firmware with Odin
- Download USB drivers for every Android brand
- How to back up your Android phone without root
- How to make a Nandroid backup in TWRP
That’s it. Grab the right KDZ, put the phone in Download Mode, run a CSE Flash, and your LG phone should boot on clean stock software.
Stuck at a certain percent or getting an error in LG Flash Tool? Leave a comment with your LG model number (like LM-G900UM) and the exact error, and I’ll help you get it booting again.
Use LGUP its better choose upgrade and after browse your kdz and voilla it works
connection failed with the server it says.
Just ignore that popup. Don’t choose “OK”. The installation will finish. Just watch your phone.