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How to block Bootloader with Fastboot on Android

Having an unlocked bootloader on Android devices very useful for several reasons, for example, for flashare firmware, installing TWRP and getting root permissions. But on the other hand, having the bootloader blocked has its advantages, such as blocking some features on the Android device due of security reasons. If for this last reason, after unlocking the bootloader and you want to re-lock Android Bootloader to avail yourself of these services, do not you know how to do it, continue reading and you will find the guide to lock bootloader on your Android device.

Google has released an update for SafetyNet that performs some checks on the phone. Among these, even the bootloader and if you encounter problems like the unlocked bootloader, you can deny access to some applications or disable certain services, such as Android Pay.

Fortunately, relocking the Bootloader solves the problem. But (obviously) you will lose all the benefits that come with the unlocked Bootloader on the device we mentioned earlier.

The Fastboot commands to relock the Bootloader are not the same for all devices. So, in the instructions below, we've put together a list of all the Fastboot commands you can use to relock the Bootloader on your device.

How to block Bootloader with Fastboot

  • configuring ADB and Fastboot on the PC. To find out how, follow the next steps:
    • Download the file ADB-setup-1.4.3.exe.
    • Double-click / Run the ADB-setup-1.4.3.exe file.
    • A command prompt window will appear with a blue background. Say s to all requests on this screen. To say yes, just type Y and press Submit.

block Bootloader adb-and-fastbootOnce ADB, Fastboot and your device's drivers are installed, the configuration window closes automatically and you get ADB functioning and Fastboot configured on your system.

  • Connect the device to the PC and open a command window on the PC.
  • Run the following boot device command in bootloader mode:
adb reboot bootloader

Now run the following commands to re-lock the Bootloader. It is not necessary to use all the commands shown below. If saying that you've tried it works, you can stop led follow the next step.

fastboot oem lock
fastboot flashing lock
fastboot oem relock
  • Once the bootloader blocked. Restart the device with the following command:
fastboot reboot

If you have performed all the steps correctly, the Bootloader will be blocked on your Android device. If you have any suggestions to add to this page, please let us know in the comments section below.