Android Bootloop: How to Fix the Boot Loop

Introduction / Why This Is Needed

Bootloop (boot loop) is one of the most unpleasant issues on Android: the phone restarts infinitely without reaching the home screen. This can be caused by a faulty update, an app conflict, or corrupted system files. This guide will help you diagnose and fix the problem yourself, starting with the simplest methods and progressing to reflashing. You can return your device to working condition without visiting a service center.

Requirements / Preparation

Before you begin, ensure that:

• The device is charged to 50% or more (connect it to a charger).
• For some steps (entering recovery, reflashing), you will need a computer with ADB and Fastboot installed (if not installed, download SDK Platform Tools from Google).
• For reflashing, you will need the official firmware (stock ROM) for your model (download it from the manufacturer's website or trusted sources).
• If you have an unlocked bootloader, be careful: reflashing may void the warranty.

Step-by-Step Instructions

Step 1: Determine the Bootloop Type and Prepare the Device

First, determine at which stage the boot process stops:

• Soft bootloop: The phone shows the manufacturer's logo, then a black screen, and the logo again.
• Hard bootloop: The device does not respond to power buttons, only vibration or a charging indicator.

If the phone does respond to buttons, try holding the power button for 10–15 seconds to force a shutdown. Then turn it on again. If the problem recurs, move on to the next steps.

Step 2: Boot into Safe Mode

Safe mode disables all third-party apps. If booting succeeds in safe mode, the problem is in installed software.

How to enter:

• On most devices: Hold the power button until the menu appears. Long-press the "Power off" option. When prompted for confirmation, hold the volume down button until the reboot completes.
• On some models (e.g., Samsung): After turning off, turn on the device while holding the volume down button until the logo appears, then release.

In safe mode, "Safe mode" will appear in the corner of the screen. If you successfully boot, uninstall recently installed apps via Settings → Apps. If you cannot access settings, use ADB:

adb shell pm uninstall -k --user 0 <package_name>

Replace <package_name> with the package name (e.g., com.example.app). You can find packages via adb shell pm list packages | grep <part_of_name>.

⚠️ Important: Safe mode does not remove system apps. If the problem is with a system update, this step will not help.

Step 3: Clear Cache Partitions via Recovery Mode

Cache can become corrupted after an update and cause a bootloop. Clearing it does not affect personal data.

Entering recovery mode:

• Turn off the device.
• Hold the button combination (usually Power + Volume Up; on Samsung — Power + Volume Up + Home). Check the specific combination for your model (e.g., for Xiaomi: Power + Volume Up).
• Release the buttons when the logo or recovery menu appears.

Clearing the cache:

1. Use the volume buttons to navigate to Wipe cache partition (or "Clear cache").
2. Press the power button to select.
3. Confirm the action (usually Yes).
4. After completion, select Reboot system now.

If the bootloop persists after rebooting, proceed to the next step.

Step 4: Perform a Factory Reset

This step will delete all data and return the system to its original state. Create a backup if possible!

In recovery mode:

1. In the menu, select Wipe data/factory reset (or "Reset data/factory settings").
2. Confirm the action (you may need to type "Yes").
3. After completion, select Reboot system now.

Alternative method (if the system boots but with a bootloop):
If you can briefly access settings (e.g., via safe mode), perform the reset via Settings → System → Reset → Factory data reset.

💡 Tip: After a reset, the first boot may take up to 5 minutes — this is normal.

Step 5: Flash Stock ROM

If none of the previous steps helped, the system partition or bootloader may be corrupted. This requires more time and caution.

Preparation:

1. Find the exact device model (e.g., SM-G991B for Samsung Galaxy S21).
2. Download the official firmware (stock ROM) for your model and region. For Samsung — via Odin, for Xiaomi — via Mi Flash, for Google Pixel — via Factory Images.
3. Extract the archive, install drivers (if needed).
4. Enable USB debugging (if still accessible) and OEM unlocking (if required). To unlock, you usually need to run the command fastboot oem unlock (this will erase data!).

Flashing via Fastboot (universal method):

# Reboot the device into fastboot mode (usually Power + Volume Down)
fastboot devices  # check connection
fastboot erase system  # delete old system partition (optional but recommended)
fastboot flash system system.img  # flash system image
fastboot flash boot boot.img      # flash bootloader
fastboot flash recovery recovery.img  # flash recovery (if needed)
fastboot reboot

Image names may vary (e.g., system.new.dat.br for compressed images). Follow the instructions provided with the firmware.

⚠️ Important: Do not interrupt the flashing process! The device may become "bricked".

Checking the Result

After each step, try to boot the device normally:

• Successful result: The home screen appears, the system fully loads.
• If booting succeeds but there are errors in specific apps — check for updates or reinstall the problematic apps.
• If the bootloop remains — proceed to the next step.

Possible Issues

Cannot enter recovery mode:

• Try other button combinations (check for your model).
• If buttons do not work, use ADB: adb reboot recovery (requires USB debugging enabled).
• If the device is completely unresponsive, there may be hardware failure (e.g., memory malfunction).

Reset did not help:

• The system partition or bootloader may be corrupted — reflashing is required (Step 5).
• Check if "Bootloop" mode is enabled (bootloop due to corrupted boot.img).

Flashing error "FAILED" or "device not found":

• Ensure drivers are installed (for Windows).
• Check the USB cable (use an original one if possible).
• Enable bootloader unlocking (if required).
• For some devices (e.g., Samsung), flashing via Odin requires "Download Mode" (not "Bootloader Mode").

Data loss:

• If you did not make a backup, recovering data after a reset or reflash is difficult. Use data recovery services (e.g., Dr.Fone) only if there is a chance, and do not write new data to the device.

Bootloop after reset/reflashing:

• The firmware may be incorrect (not for your model) or corrupted. Download the firmware again.
• Check for hardware component failure (e.g., RAM). In this case, repair is needed.

If none of the methods help, a hardware malfunction is likely (e.g., memory or processor failure). Contact an authorized service center and inform them of the steps you have already taken.