Xiaomi Mi S2 firmware: 3 proven methods + error solving

Xiaomi Mi S2 (codename siris) is a popular smartphone of 2018, which is still in active use. However, over time, official support for MIUI ends, and users face slowdowns, bugs or the desire to install custom firmware, the firmware of the device can return to its former performance, add new features or even extend the battery life.

In this guide, we will analyze all the current ways to install Xiaomi Mi S2 firmware in 2026: from official updates via MIUI Updater to install custom firmware through TWRP and Fastboot. Particular attention will be paid to unlocking the bootloader without waiting 720 hours (relevant to new Xiaomi accounts) and solving typical errors like Anti-Rollback or Invalid Image.

1. Firmware Preparation: What to Do Before You Start

Xiaomi Mi S2 firmware is a responsible process, and the wrong actions can turn your phone into a brick.

• 🔋 Charge the battery to at least 70%. Interrupting the process due to battery discharge almost always leads to a hard brick).
• 📱 Backup important data. The firmware erases internal memory (except files on the computer). SD-Use Mi Mover, Google Photos or manual copying on PC.
• 🔐 Find out the version. MIUI And the model. Go to the settings. → About the phone. Write down: Version. MIUI (for example, MIUI Global 14.0.5) Assembly number (e.g, V14.0.5.0.TFJMIXM) Device code name (siris for Mi) S2)
• 🖥️ Prepare your PC: Install the Mi Unlock Tool (to unlock the bootloader). Download ADB and Fastboot (or use the Mi Flash Tool). Disable the antivirus, it can block firmware files.

⚠️ Attention: If your Mi is yours S2 Purchased in China (market version) CN), firmware MIUI It can block the network! Check the model in Settings → The phone. → A model. CN-Use only firmware with China markings.

Also prepare a USB cable (preferably original) and check ports on your PC – unstable connection can interrupt the firmware. If you plan to install custom firmware (for example, LineageOS or Pixel Experience), additionally download:

• 📦 TWRP Recovery for siris (up-to-date version from official website).
• 📱 Firmware (official or custom) in.zip format for Recovery or.tgz for Fastboot.
• 🔑 Magisk (if you need root) - the latest version from GitHub.

Battery charge ≥70% | PC/cloud data backup | Downloaded firmware and tools (Mi Flash, ADB) | Xiaomi drivers installed on PC | Antivirus and firewall disabled | Device codename (siris) checked

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Method 2: Official update via MIUI Updater (without unlocking)

The easiest and safest method is to upgrade through the built-in MIUI Updater app, which is suitable if:

• 📲 You need to update. MIUI before the last official.
• 🔒 You are not planning to install custom firmware.
• ⚡ The loader of the device is locked (standard state).

Instructions:

1. Open Settings → About the phone → System update.
2. Click on the icon. ⋮ (three dots) in the upper right corner and select Select firmware file.
3. Specify the path to the downloaded firmware file (.zip format, the name must match your model, for example, miui_SIRISGlobal_V14.0.5.0.TFJMIXM_...).
4. Confirm the installation and wait for the restart (it will take 5-15 minutes).

If the update is stuck on the MIUI logo for more than 20 minutes:

• 🔄 Forced to restart the phone by clamping the power + Volume up for 10 seconds.
• 🔧 Repeat the process or try flashing through Recovery (method 3).

⚠️ Note: If you see a Can't verify update error during the update, the firmware file is corrupted or not suitable for your version. MIUI. Download it again from the official Xiaomi website.

💡

The official update via MIUI Updater saves all data and settings, but only works for native MIUI firmware without modifications.

Method 2: Firmware via Fastboot (with bootloader unlocking)

This method is needed if:

• 🔓 You want to install custom firmware (like LineageOS or Pixel Experience).
• 📉 Your device is “blocked” (not switched on or hung on the logo).
• 🔄 We need to revert to an older version. MIUI (for example, MIUI 14 on MIUI 12).

Fastboot requires you to unlock the bootloader. In 2026, Xiaomi tightened the rules: new accounts must wait 720 hours (30 days) after the device is tied.

Step 1: Unlock the bootloader

1. Link your device to your Mi Account: Go to Settings → Xiaomi Account and log in. Enable Settings → Additional → Developers → Unlock OEM and Debug over USB.

Connect your phone to your PC

adb devices

(Serial number of the device must be displayed).

Launch the Mi Unlock Tool

bypass

After successful unlocking, the phone will automatically reset to factory settings.

Step 2: Firmware with the Mi Flash Tool

1. Download Fastboot firmware for siris from the official website (choose the Fastboot version,.tgz format).
2. Unpack the archive in a folder without Cyrillic characters (for example, C:\MiS2_Fastboot).
3. Launch MiFlash.exe, click Select and specify the path to the firmware folder.
4. Connect your phone in Fastboot mode (clip Power + Volume down when the phone is off).
5. In the Mi Flash Tool, press Refresh and the serial number should appear.
6. Select the firmware method: Clean all - complete cleaning (recommended when changing the version of MIUI), Clean all and lock - cleaning + lock bootloader (only for official firmware!), Save user data - data storage (not always stable).

Flash

Official Update via MIUI Updater| Fastboot (Mi Flash Tool)| Installation via TWRP Recovery| LineageOS, Pixel Experience | Not stitched by yourself

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Method 3: Install firmware through TWRP Recovery

TWRP (Team Win Recovery Project) is a custom recovery that allows you to install informal firmware, make backups and get root rights. For the Xiaomi Mi S2, the current version of TWRP is 3.7.0 or later.

Step 1: Installation of TWRP

Before installing TWRP, make sure the bootloader is unlocked (see Method 2).

1. Download TWRP for siris (.img file).
2. Rename the file to twrp.img and place it in the folder with the platform-tools (where adb.exe is located).
3. Connect your phone in Fastboot mode and execute the command: fastboot flash recovery twrp.img
4. Immediately after a successful firmware, go to TWRP, holding Power + Volume up (otherwise MIUI will re-record recovery!).
5. Return to the main menu, select Install and specify the path to the firmware file.
6. Confirm the installation with a swipe and wait for completion.
7. If you install custom firmware (not MIUI), then be sure to go through it: GApps (Google services, if they are not included in firmware). Magisk (for root rights, if necessary).

Reboot → System

⚠️ Note: When installing custom firmware on Mi S2 There's a lot of encryption issues, and if you're rebooting, you're asking for it. PIN-code but does not accept it, return to TWRP and run Format Data (not Wipe!) that deletes all the data, but unlocks the system.

💡

Before installing custom firmware, check its compatibility with the codename siris on the XDA-Developers forum. Some builds may not support the camera or NFC module.

5. Solving typical firmware errors

Even if you follow the instructions, you can get errors, and we'll look at the most common ones and how to fix them.

Error 1: The phone does not turn on after the firmware ("brick")

Symptoms: black screen, no reaction to buttons, no charging indicator.

• 🔌 Connect your phone to charge for 30 minutes – sometimes it helps to “swipe” the battery.
• 🔧 Try to log in to Fastboot (Food). + Loudness down) or Recovery (Fooding + Loudness up).
• 📥 If the device is defined as a Qualcomm HS-USB QDLoader 9008 means a critical error has occurred (e.g., damaged) EMMC). In this case, only the firmware through EDL-Regime with an Authorized Account.

Error 2: Hanging on the MIUI logo or bootloop

Symptoms: The phone is constantly rebooting or hanging on the logo.

• 🔄 Go to Recovery and run Wipe Cache.
• 📦 Re-flash the same version MIUI Fastboot (Clean All Method).
• 🔧 If the problem occurred after installing custom firmware, return to the official MIUI, then repeat the process.

Error 3: Network or IMEI is not working after firmware

Symptoms: No cell network signal, IMEI has become Null/Null or 0.

• 📡 Check if the firmware is suitable for your version of the device (CN/Global).
• 🔧 Restore. IMEI assisted QCN-file (requires backup or help from a service center).
• 📶 Refuse the modem module with Fastboot: fastboot flash modem NON-HLOS.bin (file NON-HLOS.bin it's in the firmware folder).

6.Castom firmware for Xiaomi Mi S2: what to choose in 2026

Official support for the Mi S2 ended with MIUI 12.5, but the development community continues to produce custom firmware. Here are the best options for 2026:

Before installing custom firmware, consider:

• 🔋 Autonomy: Castom firmware can reduce battery life by 10-20%.
• 📸 Camera: Some firmware (like LineageOS) have a worse camera than others. MIUI.
• 🔒 Security: Absence of monthly patches from Xiaomi increases vulnerability risk.

To install any custom firmware, it is necessary:

1. Unlock the loader.
2. Set up TWRP.
3. Backup your current firmware in TWRP (Backup → System + Boot + Data).

7.How to get back the official MIUI after custom firmware

If custom firmware was unstable or you decided to return to the “native” MIUI, follow this instruction:

1. Download the official Fastboot firmware for siris from Xiaomi (select the same region version as it was originally: Global, CN or EU).
2. Unpack the firmware in the folder and delete the file flash_all_lock.bat (If it is available, the loader will be blocked!
3. Connect your phone in Fastboot mode and launch flash_all.bat (For Windows, or use manual commands: fastboot flash boot boot.img fastboot flash system system.img fastboot flash recovery recovery.img fastboot flash vendor vendor.img fastboot erase userdata fastboot reboot
4. Wait for the reboot (the first launch will take 5-10 minutes).

⚠️ Note: If you block the bootloader after returning to the MIUI (Fastboot oem lock team, custom firmware installation will be impossible without re-unlocking and waiting 720 hours!

After returning to MIUI:

• 🔄 Update the system through MIUI Updater to the latest version.
• 🔧 Restore data from the backup (if any).
• 📡 Check the network and IMEI (Restore if necessary QCN).

8. Frequently Asked Questions (FAQ)