Recover a Soft‑Bricked Android Phone Using Fastboot and ADB

1. Download the platform-tools zip for your OS from the official Android developer site.
2. Extract the archive to a location you can easily access, e.g., C:\adb on Windows or ~/adb on macOS/Linux.
3. Add the folder to your system PATH so you can run adb and fastboot from any terminal.
   • Windows: Right‑click This PC → Properties → Advanced system settings → Environment Variables → Path → Edit → New and paste the folder path.
   • macOS/Linux: Add export PATH=$PATH:/path/to/platform-tools to your ~/.bashrc or ~/.zshrc and run source ~/.bashrc.
4. Open a new terminal window and verify the installation by typing fastboot --version. You should see the version number without errors.

1. Locate the exact firmware for your device. The filename usually contains the model (e.g., Pixel_5a_2022_09_01.zip) and the Android version.
2. If the file is a .zip, extract it with any archive tool. Inside you will find a collection of .img files such as boot.img, system.img, vendor.img, and sometimes radio.img.
3. Create a dedicated folder (e.g., stock_firmware) and copy all extracted .img files there. This keeps the flashing command tidy.

1. Open Settings → About phone and tap Build number seven times. You will see a toast confirming "You are now a developer".
2. Return to the main Settings screen, open System → Developer options, and toggle USB debugging ON.

1. Power off the device completely. Hold the Power button for about 10 seconds to ensure it is truly off.
2. Enter the device‑specific fastboot key combination. Common combos:
   • Pixel/Google: Power + Volume Down (hold both until the Fastboot screen appears).
   • Samsung (ex‑Download mode): Power + Volume Up + Home (or Bixby) then press Volume Up again.
   • OnePlus: Power + Volume Up while the device is off.
3. The screen should show a text‑only interface with the Android logo and the word “FASTBOOT”. If you see a different UI (e.g., “Download mode”), you are in the wrong mode – power off and retry the correct key combo.
4. Connect the phone to your PC via the data‑capable USB cable.
5. Open a terminal on the PC and run fastboot devices. You should see a device ID like 0123456789ABCDEF fastboot. If nothing appears, try a different USB port, a different cable, or enable “USB debugging” again.

1. In the fastboot terminal, execute fastboot flashing get_unlock_ability. If the output says 0, the bootloader cannot be unlocked on that device (common on some carrier‑locked phones). In that case, you must use the OEM’s official unlocking tool or contact support.
2. If the ability is 1, run fastboot flashing unlock. The device will display a warning screen; use the volume keys to confirm and the power button to proceed.
3. After unlocking, the device will perform a factory reset automatically. This erases user data, so the backup step in the next section is essential.
4. When the screen reboots into fastboot again, you can continue.

   Some OEMs (e.g., Xiaomi, OnePlus) require you to register an unlock code on their website before the command works. Check the manufacturer’s developer portal if the generic command fails.

1. Create a folder on your PC, e.g., backup_fastboot.
2. Run the following commands, adjusting the list of partitions to match those present in your firmware package:

   fastboot flash --download-only boot boot.img
   fastboot flash --download-only system system.img
   fastboot flash --download-only vendor vendor.img
   # Add other partitions as needed, e.g., radio, vbmeta
   

   This copies the images from the phone to the PC without overwriting anything on the device.
3. Verify the files exist in backup_fastboot. Store them on an external drive before proceeding.

1. Navigate to the folder containing the .img files.

   cd /path/to/stock_firmware

2. Flash each partition in the order recommended by the manufacturer. A typical order is:

fastboot flash boot boot.img
fastboot flash vendor vendor.img
fastboot flash system system.img
# If a radio image is present, flash it next
fastboot flash radio radio.img
# Finally flash the vbmeta (verified boot) image if it exists
fastboot flash vbmeta vbmeta.img

3. Watch the terminal output. Each command should finish with OKAY. If you see FAILED, note the error message – common causes are mismatched partition sizes or a locked bootloader.
4. When all partitions are flashed, run fastboot reboot to restart the device.

   Some devices require a special command after flashing, such as fastboot flashing lock to re‑lock the bootloader, or fastboot oem lock. Check the OEM’s flashing guide for any post‑flash steps.

1. Allow the device to finish booting. The first boot after flashing can take longer (up to 2‑3 minutes) as the system indexes data.
2. Complete the initial setup (language, Wi‑Fi, Google account). If the device reaches the home screen, the unbrick succeeded.
3. Open Settings → About phone → Build number and verify the Android version matches the firmware you flashed.

1. Boot back into fastboot mode (Power + Volume Down).
2. Run the appropriate command for your device:
   • Pixel/Google: fastboot flashing lock
   • Samsung (Download mode): Use Odin to re‑lock, or follow the OEM’s fastboot command.
   • OnePlus: fastboot oem lock
3. The device will perform another factory reset. After it restarts, the bootloader is locked again.

1. Download the official OTA zip for your device. It should be the same version you intend to restore.
2. Boot the phone into recovery mode:
   • Power off, then press Power + Volume Up + Home/Bixby (or the OEM‑specific combo) until the recovery screen appears.
3. In the recovery menu, select Apply update from ADB (or similar wording).
4. Connect the phone to the PC and run:

   adb sideload path/to/ota_package.zip

   The PC will stream the zip to the device; progress is shown on both sides.
5. When the sideload finishes, choose Reboot system now. The device should boot into the freshly installed stock ROM.