How to flash Xiaomi Redmi Note 9: official and custom firmware

Xiaomi Redmi Note 9 (codenamed merlin) may need firmware to upgrade to the current MIUI, install custom firmware like LineageOS or Pixel Experience, and solve software failures. However, the process has nuances, from unlocking the bootloader to choosing the right version of software for your modification (Note 9, Note 9S or Note 9 Pro).

In this article, we will discuss all the current methods of firmware: through MIUI Updater, Recovery and Fastboot, and also consider how to avoid typical errors.

If your Redmi Note 9 is slowing down, running out quickly, or making bugs when you upgrade over the air, firmware often helps to make your device work again. But it's important to understand that any firmware is a risk. Even official Xiaomi updates sometimes contain bugs, and custom firmware can deprive you of features like the Widevine L1 (needed for watching Netflix in HD).

Preparation for firmware: what to do before the start

Before you start firmware, follow the mandatory steps, which can lead to data loss or the inability to restore the phone.

1. Create a backup. The firmware erases all data from internal memory (except for the MIUI Updater update without resetting). Use Mi Cloud, Google Photos for media files or programs like Titanium Backup (requires root).

• 📱 Contacts (export to) VCF)
• 📸 Photos and videos (transfer to PC or cloud)
• 🔑 Wi-Fi Passwords (Write down or use WiFi Key Viewer)
• 🎮 Preserve games (if you play Genshin Impact, PUBG Mobile and the like.)

2. Check the model and firmware version. The Redmi Note 9 has several modifications:

• 📱 Redmi Note 9 (merlin) — MediaTek Helio G85
• 📱 Redmi Note 9S (curtana) — Snapdragon 720G
• 📱 Redmi Note 9 Pro (joyeuse) — Snapdragon 720G (for India)

Install the wrong firmware, you get a "brick." You can find out the model in Settings → About the phone → Model or through the command:

adb shell getprop ro.product.model

3. Charge the phone at least 60%. Interrupting the firmware due to battery discharge is almost guaranteed to lead to the failure of the device. If the battery is worn out (capacity below 80%), connect the phone to charge necessarily through a USB-hub with power - directly from the PC may not be enough current.

Official Firmware Methods: MIUI Updater and Recovery

If you need to upgrade the Redmi Note 9 to the latest version of MIUI without risking losing your warranty, use official methods.They do not require unlocking the bootloader and are suitable for most users.

Method 1: Update via MIUI Updater (the safest)

1. Open Settings → About the phone → System update.
2. Click on the three dots in the top right corner and select Select Service Pack.
3. Specify the path to the downloaded firmware file (should be called type) miui_MERLINGlobal_V12.5.3.0.RJOMIXM_...).
4. Confirm the installation and wait for the reboot.

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Note: If the firmware file is larger than 2GB and the phone’s internal memory is almost full, the update may end with an error of 7.

Method 2: Installation via Recovery (if the “over-the-air” update doesn’t work)

1. Download the official firmware for your model from en.miui.com (select Recovery ROM).
2. Rename the file to update.zip and transfer it to the root of internal memory.
3. Turn off the phone, then press Power + Volume up to enter Recovery.
4. Select Install update.zip and confirm.

Download the official Recovery ROM|File renamed to update.zip|Phone's charged. >60%|Backup created-->

🔹 Important: If after the firmware through Recovery, the phone is stuck on the logo MI, Wait 10-15 minutes. Sometimes the first download takes a long time. If after that time nothing has changed, try resetting your settings via Recovery (Wipe Data).

Firmware through Fastboot: when you need to unlock the bootloader

The Fastboot method is used to install official Fastboot ROMs or custom firmware, requiring unlocking the bootloader, which resets the phone to factory settings and may take away warranty (if it still works).

Step 1: Unlock the bootloader

1. Link your Mi Account to your phone in Settings → Xiaomi Account.
2. Turn on Developer Options (7 times tap on the MIUI version in About Phone).
3. Activate OEM Unlock and USB Debugging in Settings → Additional → For Developers.
4. Download Mi Unlock Tool from the official website and unlock it (it may take 7-15 days).

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Warning: Once the bootloader is unlocked, anti-rollback will work, which means you won’t be able to return to an older version of MIUI than the one you originally installed. Check the current version in Settings → About Phone → MIUI version.

Step 2: Firmware through Fastboot

1. Download Fastboot ROM for your model (the file will be in the archive.tgz).
2. Unpack the archive in a folder on your PC (the way without Cyrillic!).
3. Connect your phone to your PC in Fastboot mode (press Power + Volume down when the phone is off).
4. Launch the file. flash_all.bat (for Windows or flash_all.sh (for Linux/Mac).

If the script gives an error waiting for the device, check:

• 🔌 Cable USB (Better to use the original)
• 🖥️ Mi Phone Manager drivers installed
• 🔄 Try another one. USB-port (preferably) USB 2.0)

Installation of custom firmware: TWRP and alternative OS

Custom firmware like LineageOS, Pixel Experience or ArrowOS offer more customization options, but require an unlocked bootloader and custom Recovery (usually TWRP) installation, a process that is more risky than official firmware, but allows:

• 🚀 Install a clean Android without shell MIUI
• 🔄 Get updates longer than Xiaomi officially supports
• 🔧 Customize the interface deeper (themes, animations, sounds)

Step 1: Installation of TWRP

1. Download the current version of TWRP for Redmi Note 9 (merlin) from twrp.me.
2. Rename the file to twrp.img and place it in the folder with the platform-tools (from the Android SDK).
3. Connect your phone in Fastboot mode and execute the command: fastboot flash recovery twrp.img fastboot boot twrp.img

Step 2: Firmware custom OS

1. Download firmware (e.g. LineageOS 20 for merlin) and GApps (if you need Google services).
2. Transfer files to your phone or flash drive (FAT32!).
3. In TWRP, run Wipe → Advanced Wipe and mark Dalvik, Cache, System, Data.
4. Install firmware, then GApps, then (if necessary) Magisk for root.

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Note: After installing custom firmware may stop working: 📷 Wide-angle camera (requires separate fixes) 🔐 Banking applications (due to lack of SafetyNet) 🎬 Netflix HD (Widevine loss L1) Some of the problems are solved by installing Magisk and modules like Universal SafetyNet Fix.

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Before installing custom firmware, check on the XDA-Developers forum to see if there are any bugs specifically for your model. For example, some LineageOS builds for Redmi Note 9 don't have NFC or proximity sensors working.

Common mistakes and their solutions

Even when you follow instructions, you can have errors, and here are the most common problems and ways to fix them.

Critical: If, after a failed firmware, the phone doesn't respond to any combination of buttons and is not detected by the PC, it's a "hard brick." It can only be restored through a hard brick. EDL-Mode (requires an authorized Xiaomi account or contacting a service center).

How to return the official firmware after custom

If custom firmware is unstable or you need a warranty, you can return to the official MIUI.

1. Download Fastboot ROM for your model from the official website.
2. Unpack the archive and launch it. flash_all.bat (For Windows, use the Mi Flash Tool.
3. In the Mi Flash Tool, select the clean all option.
4. After firmware, the phone will automatically restart and start setting up as new.

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Note: If you have installed custom firmware with a modified vendor or persist partition, the official firmware may not stand up. In this case, you need firmware through EDL (power users only!).

After returning to MIUI, you may need to re-unlock the bootloader (if you want to install custom firmware again).

• 📶 Communication modules (Wi-Fi, Bluetooth, mobile network)
• 📸 All cameras (main, wide-angle, macro)
• 🔋 Charging (sometimes after firmware disappears fast charging)

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You can return to the official firmware at any time, but if you changed partitions of the disk (for example, when installing LineageOS), you may need firmware through EDL - this is a difficult procedure, it is better to contact the service.

FAQ: Frequent questions about the Redmi Note firmware 9