[Development] How to unlock the Bootloader of an Android phone via Fastboot

[hovatek]

Unlike in some other devices, you don't necessarily need to unlock the bootloader to flash a custom ROM to your Mediatek (MTK), Spreadtrum (SPD) Android phone. You don't even need bootloader (fastboot) to flash a custom recovery since Mediatek has SP Flash tool and Spreadtrum has Research / Upgrade download tool amidst several Chinese boxes. There are however certain scenarios where fastboot is the only feasible way to get a custom recovery loaded to your device from which you can then root, backup or install a custom ROM. This guide will explain how to unlock the Bootloader on a Mediatek (MTK), Spreadtrum (SPD) or Qualcomm (QLM) Android phone, an important prerequisite for flashing a custom recovery via fastboot.

Requirements

• Setup ADB-Fastboot on your PC. For Spreadtrum devices, follow this guide (in order to enable adb detect your device)
  
• Enable USB Debugging and OEM Unlocking (if available)
  

How to unlock a Mediatek, Spreadtrum or Qualcomm Android phone's Bootloader via fastboot

Follow the steps below to unlock the Bootloader of an Android device

1. Open the adb folder
   
   
   
   
2. Hold Shift (on the keyboard) then right-click on a blank space in the folder > Select Open Command window here
   
   
   
   
3. Command prompt screen (adb) should now be open
   
   
   
   
4. Connect the phone to PC (via USB cord) while ON then run the command below (by "run", I mean type then press Enter
   
   Code:

   adb devices
   
   
   
   
5. If you've setup everything right, the device should get detected under List of devices attached
   
   
   
   
6. Run the command below to get the phone into Bootloader (fastboot)
   
   Code:

   adb reboot-bootloader
   
   
   
   
7. The phone should now boot into fastboot
   
   
   
   
8. In fastboot, test detection / connection to the device using
   
   Code:

   fastboot devices
   
   
   
   
9. If fastboot is set up right, you should see its ID printed out
   
   
   
   
10. Now, check the phone's Bootloader status (if its locked or unlocked)
    
    Code:

    fastboot getvar unlocked
    
    
    
    
11. If the Bootloader is already unlocked then you should see "Unlocked"; you can stop following this guide from here.
    
    
    
    
12. If the Bootloader is still locked, you should see Unlocked: no
    
    
    
    
13. Run the command below to unlock Bootloader
    
    Code:

    fastboot oem unlock
    
    
14. If that doesn't work then try
    
    Code:

    fastboot oem unlock-go
    
    
    
    
15. You should get a prompt (on the phone) asking you to press Volume up to  confirm or Volume down to cancel. Press Volume up on the phone (for some phones its actually the opposite; Volume down would confirm while up would cancel or do nothing)
    
    
16. Once Bootloader is unlocked, reboot the phone using
    
    Code:

    fastboot reboot
    
    
17. The phone might take a while to boot up (since its a first boot) so be patient
    

Important Notice

• This guide isn't guaranteed to work on all Mediatek, Spreadtrum & Qualcomm Android phones
  
• Ensure to backup your important stuff because unlocking your Bootloader wipes your phone's data (/userdata)
  
• Unlocking the bootloader bricks some devices so ensure to relock or flash the firmware if you find yourself in such a situation
  
• If you successfully installed ADB / fastboot and your device still isn't detect then its most likely due to old ADB, fix it using the guide here
  

[sparleta]

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[freshtyt]

Hi guys,I have been using the step by step guide to unlock my Infinix Hot5 Model X559C. Unfortunately, once i send the code to unlock bootloader the screen pops out on my phone but does not respond to either Volume Up/Down or Power button. What could be the case? Attached is the image where it hangs

did you enable oem unlocking in settings before trying to unlock?
and why are you trying to unlock bootloader?

[slichy]

i have been following the instructions to unlock my leagoo t5c. my phone is detected in adb, but when i want to reboot in bootloader using adb reboot bootloader, my phone stuck in boot logo. and when i checked in fastboot devices, is showed the message <waiting the devices>. whats wrong with my phone ? i have installed the driver clearly. my phone is use spreadtrum sc 9853i. thanks before

[hovatek]

i have been following the instructions to unlock my leagoo t5c. my phone is detected in adb, but when i want to reboot in bootloader using adb reboot bootloader, my phone stuck in boot logo. and when i checked in fastboot devices, is showed the message <waiting the devices>. whats wrong with my phone ? i have installed the driver clearly. my phone is use spreadtrum sc 9853i. thanks before

Boot into recovery mode and check if there's an option to boot into Bootloader from there

[paeffiong]

Nice and well detailed. Could you please attach a video cos there are so many who learns faster when taught with a video tutorial.

[arip jumaing]

Nice and well detailed. ADB AND FASTBOOT MODE FOR UBL..THANKS

[Muhanad Samaty]

guys everything went well except rightnow how do i install supersu.zip when i dont have twrp or philz recovery for my phone ,, im using Tecno CX AIR build number : cxair-H3713A-N-171207V139 please help.

[hovatek]

guys everything went well except rightnow how do i install supersu.zip when i dont have twrp or philz recovery for my phone ,, im using Tecno CX AIR build number : cxair-H3713A-N-171207V139 please help.

Use our TWRP or Philz porter @ https://forum.hovatek.com/forum-39.html

[belinda1093]

Great post, I am a newbie and it took me two days to get this far. I use both linux and windows and first a lot of problems with the adb fastboot drivers...and all the familiar problems. Then after much hassle I found out that my bootloader is already unlocked and I thought it wasn't.
Now my biggest issue is that I cannot find a suitable custom ROM for my phone (strange device I have, a Mango C9 android marshmallow, kernel 3.10.65 (!) with quad core chipset). So I should learn how to port a Rom, but I am in a hurry because I started this whole process because my phone has a virus in android system file. So I have to completely wipe it clean. I cant find a stock rom either. What would your advice be?