Reflashing Xiaomi Redmi Note 9S: 3 proven methods and expert advice

Why do owners of Redmi Note 9S decide to reflash the smartphone?

Smartphone Xiaomi Redmi Note 9S (codename curtana) was released in 2020, but still remains popular due to balanced characteristics: Snapdragon 720G processor, 48-MP camera and a capacious battery for 5020 mAh. However, over time, even such “iron” begins to slow down due to outdated software, heaping system processes or manufacturer limitations.

The main reasons for reflashing the Redmi Note 9S are:

• 🚀 An outdated version MIUI — Official updates have stopped coming out, and new features (such as HyperOS) are not available.
• 🐢 Slowdown – lags when opening applications, long system load after turning on.
• 🔓 Manufacturer restrictions – bootloader lock, inability to remove built-in Xiaomi apps.
• 🛡️ Security – no security patches for older versions of Android 10/11.
• 🎯 Custom firmware – wanting to install LineageOS, Pixel Experience or AOSP for pure Android.

But before we get started, it's important to understand that flashing is not just an update through Settings; it's a deep interference with system files that can both revive a smartphone and turn it into a brick. On the Redmi Note 9S, unlocking the bootloader erases all data without the possibility of recovery, even if the process is interrupted by 99%.

Preparation for firmware: what to do before the start

Unprepared firmware is a major source of problems, and to avoid errors like fastboot: error: Failed to boot into fastbootd or endless download on the MI logo, follow these steps:

• 📱 Check the model and version MIUI: Go to Settings. → The phone. → Version. MIUI. Write down the current firmware (for example, MIUI Global 12.5.3 Stable) Make sure that the Redmi Note is the model 9S (Curtana, not Note 9 Pro (joyeuse!
• 🔋 Charge the battery to 60-80%. If the discharge is below 30% during firmware, the device may shut down.
• 💾 Make a backup: Use the settings → Additionally. → Backup and reset → Local backup: Copy important files (photos, contacts) to your PC or cloud, and when you unlock the bootloader, the data will be erased.
• 🖥️ Prepare your PC: Install Xiaomi drivers (official website). Download the Mi Flash Tool (for Fastboot firmware) or OrangeFox/TWRP (Disable the antivirus, it can block firmware files.

If you plan to install custom firmware (for example, LineageOS), you will additionally need:

1. Unlock the bootloader through the Mi Unlock Tool (more on this below).
2. Install an alternative recovery (TWRP or OrangeFox)
3. Download firmware compatible with curtana (check out the XDA Developers or 4PDA forums).

⚠️ Attention: On the Redmi Note 9S Android 11+ Unlocking the bootloader requires you to tie your Mi Account to the device for 72 hours. If you drop your phone before unlocking, you'll have to wait again.

Method 1: Firmware via MIUI Updater (without unlocking the bootloader)

This is the safest method, but it’s only suitable for official Xiaomi updates.If you want to upgrade from MIUI 12 to MIUI 13 or update security patches, this is the way for you.

Step-by-step:

1. Download the firmware from the official website: Go to the Xiaomi download page. Select the Redmi Note 9S (curtana) model. Download the Recovery ROM (not Fastboot!).

miui_CURTANAGlobal_V13.0.1.0.SJWMIXM_...

Update

Updater

Select a firmware file

Select the downloaded file and confirm the installation.

It takes 5-10 minutes, and after the reboot, the phone will be with the new version of MIUI, but all the data will be saved.

⚠️ Note: If after the update the phone is stuck on the logo MI For more than 15 minutes, reset via Recovery: Squeeze the power + Volume up to enter Recovery Mode. select Wipe Data → Wipe All Data. Repeat the firmware after the reset.

Method 2: Fastboot firmware (official firmware with unlock)

This method is needed if:

• 🔄 You want to go back to the old version. MIUI (downgrade).
• 🚨 The phone is not switched on or stuck on loading.
• 🔓 You are planning to unlock the bootloader for custom firmware.

Step 1 Unlocking the bootloader

1. Connect your Mi Account to your phone: Go to Settings → Xiaomi Account and log in. Enable Settings → Additional → Developers → Unlock OEM. Connect your phone to your PC and confirm unlocking in Mi Unlock Tool.

Xiaomi

Fastboot

Food + Volume Down

Mi Unlock Tool

Step 2: Firmware via Mi Flash Tool

1. Download Fastboot ROM for Redmi Note 9S from the official website.
2. Unpack the archive in a folder without Cyrillic characters (for example, C:\curtana_fastboot).
3. Open the Mi Flash Tool, press Select and point the path to the firmware folder.
4. Connect your phone in Fastboot mode (a screen with a rabbit and the words Fastboot).
5. In the Mi Flash Tool, choose Clean all (full reset) or Clean all and lock (reset + lock the bootloader).
6. Press Flash and wait until it is completed (5-10 minutes).

💡

If the Mi Flash Tool doesn’t see the phone, try running it on behalf of the administrator or use an alternative program called XiaoMiTool V2.

Method 3: Install custom firmware through TWRP

For enthusiasts who want a clean Android without a MIUI shell, firmware like LineageOS, Pixel Experience or ArrowOS will work.

1. Unlock the bootloader (see Method 2).
2. Install custom Recovery (TWRP or OrangeFox)
3. Download firmware compatible with curtana.

Step 1: Installation of TWRP

1. Download the latest version of TWRP for Redmi Note 9S from the official website.
2. Rename the file to twrp.img and place it in the folder with fastboot.
3. Connect your phone in Fastboot mode and execute the command: fastboot flash recovery twrp.img fastboot boot twrp.img

Step 2: Install custom firmware

1. Download firmware (like LineageOS 20) and GApps (if you need Google services).
2. Transfer files to your phone via MTP to TWRP.
3. In TWRP, run: Wipe → Advanced Wipe (tag Dalvik, Cache, System, Data). Install → select firmware → Swipe to confirm. Repeat for GApps (if necessary). Reboot → System.

⚠️ Attention: On the Redmi Note 9S Android 12+ You may need to disconnect AVB 2.0 before installing custom firmware. TWRP Do it: fastboot --disable-verity --disable-verification flash vbmeta vbmeta.img (file vbmeta.img usually comes with a firmware).

How to return the official MIUI after custom firmware

If the experiment with LineageOS or AOSP did not meet expectations, you can return to stock MIUI.

1. Download Fastboot ROM for Redmi Note 9S (see Method 2).
2. Connect your phone in Fastboot mode.
3. In the Mi Flash Tool, select Clean all and lock, which will return stock Recovery and block the bootloader.
4. After firmware, the phone will automatically reset to factory settings.

If Google Pay or other services are not working after returning to MIUI, check the SafetyNet status in the Magisk app (if installed).

• 🔹 Remove Magisk (if installed).
• 🔹 Reset via Fastboot with the lock option.
• 🔹 Install the official firmware without modifications.

Frequent mistakes and their solutions

Even with the correct following of the instructions, problems can arise, and here are the most common ones and ways to fix them:

If none of these methods worked, try:

• 🔄 Change the Mi Flash Tool version – some firmware requires an older version of the program (for example, 2018.5.4.0).

💡

If the phone doesn’t turn on and doesn’t respond to buttons after firmware, don’t panic: plug it into charging for 30 minutes, then try logging into Fastboot (clamp Power + Volume down for 10-15 seconds).

FAQ: Answers to Frequent Questions