The bootloader is the first thing a device hits, which tells the OS of the device to launch with the required resources and, after this, all the necessary programmes startup. Similarly, Fastboot or Bootloader mode comes in handy when we have to perform a certain task.

As for regular users, they use it to flash the stock ROM through Fastboot by flashing the TWRP Zip file. Since it is quite useful for updating devices or downgrading the device itself, On the other hand, some people with advanced knowledge prefer to do custom ROM flashing to use their device to its full potential.

Meanwhile, flashing custom ROMs does come in handy after the OEM ends the software support for the device. Used to flash custom recovery such as TWRP and other zip files such as Magisk Module, factory reset or wipe specific partitions, unlock the bootloader on Android, and add advanced functionality.

Booting
in Fastboot Mode from Recovery

There are three different ways to boot into recovery from Fastboot mode for TWRP and Stock Recovery. While proceeding, you can either go with the key combination or rely on the Universal ADB and Fastboot commands.

Since there are a lot of android smartphones available, it is not easy to remember every android device key combination. Rather, it is easier when you perform it through the Fastboot commands. Before proceeding ahead, check the pre-requirements.

Prerequirements

  • Download and install the Android SDK (Special Development Kit) Platform Tool. It is required for you to install in order to do ADB and for Fastboot binary files.
  • Enable USB Debugging by enabling Developer mode. Open the advanced settings and toggle the USB debugging toggle under developer settings.)

  Booting an Android device into Fastboot

  • Connect your device with the USB Cable to your PC and then Open the Platform-tool folder where you have extracted.
  • On the folder page, type the CMD in the address bar and hit enter to open the CMD (Command Prompt).
  • Execute the adb reboot bootloader and enter to boot your device into the Fastboot.
  • After this you can perform certain task, you want to perform on your device.

Using Fastboot to boot an Android device

  • Likewise, open the Platform-tool folder and open CMD by typing the CMD in the address bar.
  • Type the fastboot reboot recovery into CMD to boot your device into the recovery mode.
  • Next, execute the fastboot boot twrp.img and then hit enter which will install the TWRP but device with A/B partition doesn’t comes with recovery partition so you need to temporarily install to boot your device into recovery via boot paration and then use the same command to permanently install.
  • Meanwhile. Device without A/B partition you can use the fastboot flash recovery twrp.img.

Flashing TWRP to the Boot Partition

  • Starting with opening the CMD from the platform-tool folder, and then execute the fastboot flash boot twrp.img.
  • Next, enter the fastboot reboot recovery which will directly boot your device to TWRP recovery.
  • you have to navigate to Wipe and then choose Format data in order to decrypt the data partition.
  • Now you can share the data between your computer to PC using the preffered method to install or flash the data on your device.
  • Once it finishes, you can reboot your device from the system sub-menu.