How to flash Xiaomi Mi 3S: official and custom firmware (2026)

Xiaomi Mi 3S (codename armani) is the legendary smartphone of 2014, which is still used by enthusiasts due to the ability to install modern firmware. However, the firmware of this device has nuances, from unlocking the bootloader to choosing compatible software. In this article, we will analyze all the current ways of firmware Mi 3S in 2026, from the official MIUI to custom builds based on Android 10/11.

It is important to understand that the Mi 3S belongs to the first generation of Xiaomi devices with a Qualcomm Snapdragon 800 processor (MSM8974AB). This imposes restrictions on the choice of firmware: for example, LineageOS 18.1 (Android 11) works stably, but newer versions can slow down. Also note that after firmware you may need to re-assign your Mi Account account - especially if you use official software.

1. Firmware Preparation: What to Do Before Starting

Xiaomi Mi 3S firmware requires pre-preparation, otherwise the risk of “bricking” the device increases significantly. Start by checking the current version of the firmware: go to Settings → About Phone → MIUI Version. If the version is older than MIUI 8, first update through MIUI Updater – this will simplify further manipulation.

Mandatory steps before the firmware:

• 🔋 Charge your phone at least 70% – when discharged during firmware through Fastboot, the device can turn into a “brick".
• 📱 Make a backup of the data through Settings → Additionally. → Backup and reset or by TWRP (if established).
• 🖥️ Install Qualcomm drivers and ADB/Fastboot For Windows, Google's Platform Tools suite will do.
• 🔓 Unlock the bootloader (unless done before) without it custom firmware cannot be installed.

On the Mi 3S, this process takes up to 72 hours due to Xiaomi’s policy: after sending a request through the Mi Unlock Tool, you need to wait for confirmation via SMS. If you have already unlocked the bootloader before, check the status of the command:

fastboot oem device-info

In the answer, look for the line Device unlocked: true. If it is false, unlock is mandatory.

2. Method 1: Firmware via MIUI Updater (official method)

The safest way to upgrade the Mi 3S is to use the built-in MIUI Updater, which is suitable for migrating to a new version of MIUI without losing data, but only works with official firmware. Importantly, if your device is already on custom firmware, this method does not work, you will need to return to the drain Recovery.

Instructions:

1. Open Settings → About the phone → System update.
2. Click on the three dots in the upper right corner and select Select the firmware file.
3. Download the official firmware for armani from en.miui.com (select the version for your region: Global, China or EEA).
4. Transfer the.zip file to the phone’s root folder and select it from MIUI Updater.
5. Confirm the installation and wait for the restart (it will take 5-10 minutes).

If the update has been stuck on the Mi logo for longer than 15 minutes, don’t panic – that’s OK for the Mi 3S. But if the process lasts more than 30 minutes, try forcefully restarting the device with the Power + Volume Up button.

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If MIUI Updater does not see the downloaded firmware, rename the file to update.zip And put it in a folder. /downloaded_rom internal.

3. Method 2: Fastboot firmware (for official and custom ROM)

Fastboot is universal: it is suitable for installing both official firmware from Xiaomi and custom ones (for example, LineageOS or Pixel Experience), the main advantage is the ability to flash the device even if it does not turn on (for example, after a failed update), but there is a risk: if you choose firmware not for armani, the phone will turn into a “brick”.

Step-by-step:

1. Download the firmware in.tgz (official) or.zip (custom) format and unpack it in a folder from fastboot.
2. Turn off your phone and press Volume Down + Power to enter Fastboot mode (a hare in a hat-eared hat will appear).
3. Connect the device to the PC and check the connection command: fastboot devices If the response appears serial number – the connection is established.
4. For custom - use commands from the instructions to the firmware (usually it is fastboot flash boot, fastboot flash system, etc.).
5. Upon completion, type in fastboot reboot

If the firmware on Fastboot ended with a FAILED error (remote: partition table doesn't exist), then you are trying to flash an incompatible version. For Mi 3S, only firmware with the armani mark in the file title is suitable.

Downloaded the correct firmware for the armani| model

bootloader Unlocked (Device unlocked: true) |

Install ADB/Fastboot drivers on PC|

Charged the phone at least 70% |

Backup of important data.-->

Method 3: Install custom firmware via TWRP

For enthusiasts who want to install LineageOS, Pixel Experience or Havoc OS, the only option is firmware via TWRP. This method gives full control over the system, but requires a custom Recovery pre-installed. Importantly, only TWRP 3.6.0 or later is suitable for the Mi 3S - older versions may not support modern firmware.

How to Sweat Through TWRP:

1. Download the latest version of TWRP for armani from twrp.me.
2. Install TWRP via Fastboot: fastboot flash recovery twrp-3.6.0-armani.img fastboot reboot recovery
3. In TWRP, run Wipe → Advanced Wipe and mark Dalvik/ART Cache, System, Data, Cache.
4. Transfer the firmware (e.g. lineage-18.1-armani.zip) to your phone via MTP (TWRP has the option Mount → Enable MTP).
5. Install the firmware through Install → Select a file → Swipe to Confirm Flash.
6. After installation, run GApps (if you need Google services) and Magisk (for root rights).

Critical feature of Mi 3S: if after firmware custom ROM phone does not turn on, try to flash the kernel separately command fastboot flash boot.img (the boot.img file usually comes with firmware).

5. Unlocking the bootloader on Xiaomi Mi 3S: a step-by-step guide

Without unlocking the bootloader, you can't install custom Recovery or firmware. 3S This process consists of two steps: linking the Mi Account to the device and actually unlocking through the Mi Unlock Tool. SIM-Card with the number to which the Mi Account is linked (otherwise SMS codeless).

Instructions for unlocking:

1. Enable USB debugging: Settings → About Phone → MIUI version (click 7 times), then Settings → Additional → For Developers → Debugging over USB.
2. Link the device to your account: Settings → Mi Account → Link the device.
3. Download the Mi Unlock Tool from the official website and launch it on behalf of the administrator.
4. Sign in to the program under the same account as on the phone.
5. Connect your phone in Fastboot mode and press Unlock.
6. Wait for the confirmation SMS (can come in 24-72 hours).

If the Mi Unlock Tool is a Cann't unlock error or Current account is different from the account info on the device, then:

• 🔄 You are logged into another account on your PC and phone.
• 📱 Device not tied to account (check Settings) → Mi Account).
• ⏳ It has been 72 hours since the last attempt to unlock the device.

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Unlocking the bootloader resets all the data on the phone!

6. Solving common firmware errors

The Xiaomi Mi 3S firmware is often accompanied by errors, especially if the device is old or has been experimented with before.

If after the firmware Mi 3S does not SIM-The card is most likely missing the modem module:

1. Download the stock firmware for your region.
2. Remove the modem.img and nvram.img files.
3. Fastboot: fastboot flash modem modem.img fastboot flash nvram nvram.img

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If after installing custom firmware does not work camera, download and stitch separately module camera_blobs.zip armani.

7.How to get back the MIUI stock firmware

If custom firmware experiments fail, you can always go back to the official MIUI, which requires.tgz stock firmware and MiFlash. Importantly, you can only get back the stock firmware through Fastboot, because MIUI Updater won't work if you have custom ROM installed on your phone.

Instructions for returning to MIUI:

1. Download stock firmware for armani from the Xiaomi Firmware Updater website.
2. Unpack the archive in a folder with MiFlash.
3. Run MiFlash.exe on behalf of the administrator.
4. Connect your phone in Fastboot mode.
5. In MiFlash, press Refresh – the device must be determined.
6. Select the firmware folder and press Flash.
7. Wait until the end (green sign of success).

If MiFlash is making a mistake flash_all_except_storage.bat failed, try it:

• 🔄 Rename the file flash_all.bat into flash_all_except_storage.bat and launch it.
• 📁 Delete the file userdata.img from the firmware folder (the data will not be erased).
• 🔌 Try another one. USB-port.

8.Optimize the Mi 3S after firmware

After successful firmware, the Xiaomi Mi 3S requires additional customization for stable operation, especially for custom firmware based on Android 10/11, which can slow down on old hardware.

To improve productivity:

• ⚡ Turn off animation: in Settings → The phone. → Version. MIUI (Click 5 times on "Kernel Version" and then on Settings → For developers, install Windows animation = 0.5x.
• 🗑️ Limit background processes: Settings → Annexes → Limitation of background processes → Max. 2 process.
• 🔄 Use lightweight alternatives to standard applications (e.g. Nova Launcher instead of the standard ones). MIUI Launcher).
• 🔋 Turn off synchronization of unnecessary accounts: Settings → Accounts. → Synchronization.

For custom firmware (LineageOS, Pixel Experience):

• 📱 Install FrancoKernel or ElementalX kernel for better CPU frequency management.
• 🔧 Set up. CPU Governor on-demand or interactive via Kernel Adiutor.
• 🚫 Turn it off. ZRAM (if included, on Mi 3S He's just slowing down the system.

Note: If your phone gets too hot after you have installed LineageOS or other custom ROM, check the kernel settings. Most likely, Performance Governor is enabled, switch to Powersave or Balanced.

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On the Mi 3S with custom firmware, it is recommended to turn off hardware acceleration in the Chrome browser (in the settings, the Override software rendering list flag).

FAQ: Frequent questions about the firmware Xiaomi Mi 3S