The Xiaomi Redmi Note 4X (codenamed mido) remains one of the most popular smartphones for firmware experiments years after its release, and the reasons are obvious: reliable hardware (Snapdragon 625, 3/4 GB of RAM), removable battery and active support from the developer community. However, flashing this device has nuances that can turn the process into a nightmare for beginners, from eternal locking the bootloader to “brick” if you choose the wrong vendor file.
This article will not just take you Step-by-step to reflash the Redmi Note 4X, but also explain why each step is important. We'll take the official and custom firmware, get around the pitfalls of anti-rollback, and give you a checklist to check the device before you start. If you're looking for a way to bring your phone back to life after a failed update, or if you want to install LineageOS, here's the latest methods for 2026.
1. Preparation for flashing: what you need to know before you start
Redmi Note 4X flashing requires not only files and tools, but also an understanding of the risks, the main one being locking the bootloader after a failed attempt. Xiaomi introduced an anti-rollback (ARB) mechanism that can permanently lock the device if you install firmware with an older version of ARB than the current one. For example, if the phone is running a MIUI 12 with an ARB 4, and you try to put a MIUI 9 with an ARB 2, you get a brick.
To avoid this, always check the ARB version of the current firmware, and you can do this through the engineering menu:
- Open the Phone app.
- Enter the code ##4636##.
- Go to the Phone Information tab and find the Anti Rollback bar.
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If the engineering menu doesn’t have ARB information, check the firmware version in Settings → About Phone → MIUI version. Match it against the ARB compatibility table on the XDA Developers forum.
Another critical aspect is unlocking the bootloader, which you can't install customized backups or firmware without. Xiaomi officially allows unlocking, but it can take up to 720 hours (30 days) of waiting because of security policies. If you bought the phone with your hands, make sure the bootloader is already unlocked, otherwise you'll have to wait.
2. firmware selection: official MIUI vs custom builds
On the Redmi Note 4X, you can install three types of firmware:
- 📦 Official. MIUI — Xiaomi stable and development versions, suitable for a return to the runoff state.
- 🛠️ Castomy on the base MIUI (for example, MIUI EU, MIUI Pro – with remote Chinese services and additional features.
- 🐧 AOSP-Firmware (LineageOS, Pixel Experience, Havoc-OS) – “clean” Android without a shell MIUI.
If you want maximum stability and support for banking applications (for example, Sberbank Online or Tinkoff), stop at the official MIUI. For experiments with the interface and additional chips, custom builds based on MIUI will suit. And if you want to get rid of advertising and unnecessary Xiaomi services, look at LineageOS or Pixel Experience.
| Type of firmware | Pluses | Cons | Recommendation |
|---|---|---|---|
| Official MIUI | Stability, OTA-Updates, support for banking applications | Advertising, unnecessary services, limited customization | For everyday use |
| MIUI EU | No Ads, Weekly Updates, Advanced Settings | There may be bugs, there is no Russian language in some assemblies | For tweak lovers. |
| LineageOS | Clean Android, no unnecessary services, long-term support | Some functions may not work (for example, IR-port) | For advanced users |
Important: The firmware for Redmi Note 4 (codename nikel) is not compatible with Redmi Note 4X (mido)! Installing the wrong firmware will lead to a “brick”.
3. Unlocking the bootloader: step-by-step instructions
Without an unlocked bootloader, you won’t be able to install customized backups or firmware. Xiaomi requires an account to be linked to the device and wait for 7 days (sometimes longer).
- Link your Mi Account to your phone: Go to Settings → Mi Account. Sign in (if not, sign up). Enable Device Search and Sync.
- Activate Developer Mode: Go to Settings → About Phone. Click 7 times on the MIUI Version until the “You’re a Developer” notification appears.
Allow the OEM to be unlocked
- Back to Settings → Additionally. → For developers.
- Enable OEM Unlock and USB Debugging.
- Press Install, select a firmware file and confirm the installation.
- In the Mi Flash Tool, select the downloaded firmware and press Refresh. The device must determine how to use the device. COM-port.
- Press Flash and wait until the process is completed (10-15 minutes).
If your PC doesn’t see your phone in EDL, try:
- 🔌 Use the original USB-Xiaomi.
- 🖥️ Install Qualcomm drivers HS-USB QDLoader 9008 manually.
- 🔧 Connect the phone through USB-externally powered hub (sometimes helps with port problems).
⚠️ Attention: Recovery through EDL It drops the anti-rollback back to factory status, if you try to install the firmware with the newer version after that. ARB, The phone is locked again.
8.Optimization after firmware: what to do first
After a successful firmware, do not rush to use the phone - first follow a few important steps:
- 🔄 Reset the settings (if you have stitched custom). MIUI or AOSP): Go to Settings. → Additionally. → Recovery and discharge.
- 🔒 Set up the lock: if you have flashed LineageOS, install PIN or a graphical key before the first Wi-Fi connection, otherwise the encryption may not work properly.
- 📱 Check it out. IMEI: Enter the dialer *#06#. IMEI missing - restore EFS backup.
- 🔋 Calibrate the battery: discharge the phone before turning off, then charge to 100% without interruptions.
For AOSP-Firmware is additionally recommended:
- Install Magisk for root rights (if necessary).
- Set up ViPER4Android to improve sound.
- Disable unnecessary Google services via ADB: adb shell pm uninstall -k --user 0 com.android.chrome
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If the battery goes down quickly after the LineageOS firmware, turn off the AOD (Always On Display) function in the screen settings. It is not optimized for the Redmi Note 4X and drains the battery very much.