Unlocking bootloader is an essential step in the process of modifying system partitions such as flashing TWRP recovery. Locked bootloader prevents users from loading or flashing custom firmware into their devices. 

Most of the phones with locked bootloaders can be officially unlocked by following a guide on the OEM's website.

This usually consists of submitting your phone's Device ID and IMEI and getting a device-specific unlock code which is then used in the “fastboot” command in order to authorize the unlocking process.  

In this article, we will focus on the general process of unlocking bootloaders without specific steps on how to do so provided by the manufacturer. 

Keep in mind that unlocking the device's bootloader may void your warranty.
We recommend storing all the data first since some devices wipe their data once their bootloader is unlocked.

How to

  1. Install ADB and Fastboot on your PC
    (we recommend using Minimal ADB and Fastboot as it is lightweight, comes in a simple installation package and does the job perfectly)

  2. Enable developer options by navigating to Settings - About phone and clicking on "Build number" seven times.

  3. Go to developer options and enable the "OEM unlock" option as well as "USB debugging"

4. Connect the phone to your PC and open a command-line window as an administrator from the folder where you have your ADB and Fastboot installed. 

5. Type "adb devices" into the command line to see if your device is recognized by ADB.

6. Type “adb reboot bootloader” into the command line wait until your device reboots into Fastboot mode.

7. Once your phone reboots into fastboot mode, type the "fastboot OEM unlock" command and press Enter.

8. Confirm the action on your phone's screen (if prompted).

9. After the process has finished, you can type "fastboot reboot" to boot your phone back into Android or proceed straight to flashing a custom recovery. 

Flashing custom images onto Samsung phones is done by Odin which means you only need to enable the "OEM unlock" option and proceed straight to the flashing process.
Find out more in our article on How to flash TWRP on Samsung devices (ODIN method).