Xiaomi Redmi S2 (codename ysl) is a budget smartphone of 2018, which is still popular today due to its reliability and the ability to install modern firmware. However, over time, the original MIUI begins to slow down and updates from the manufacturer stop, in which case the firmware becomes the only way to return the device to performance or install the current version of Android.
This article will help you understand how to flash Redmi S2 in different ways: through Fastboot, Recovery or using Mi Flash Tool. We will look at the official firmware from Xiaomi, custom builds based on LineageOS or Pixel Experience, as well as the nuances of unlocking the bootloader. Importantly, the procedure requires care - errors can lead to a "brick" of the device (complete failure), if you do not follow the sequence of actions.
Before you start, check your phone model in settings (Settings → About Phone → Model). Make sure it is a Redmi S2 (ysl) and not another modification (for example, Redmi 6 or Redmi Note 5), as the firmware for them is incompatible.
1. Firmware Preparation: What to Do Before Starting
Firmware isn't just an update through a phone menu; it's a complete overwriting of system files that can cause the device to lose data or crash if something goes wrong, so it takes the lion's share of the time to prepare.
Here is the checklist before starting:
Make a backup copy of all data (photos, contacts, messages)
Check the battery power (minimum 60%)
Download the correct firmware version for the ysl model
Install Xiaomi drivers on PC (Mi PC Suite or manually)
Connect the original USB-cable (do not use cheap analogues)
Disable the antivirus on your computer (it can block firmware files)
Unlock the bootloader (if you plan to install custom firmware)-->
Pay special attention to unlocking the bootloader. Xiaomi blocks this feature by default, and you will need to activate it:
- Link your Mi Account to your phone (Settings → Xiaomi Account)
- Apply for unlocking via Xiaomi’s official website (can take up to 72 hours).
- Use the Mi Unlock Tool to complete the process.
⚠️ Note: If you are flashing a phone with a locked bootloader, the official firmware through Fastboot will install, but custom - not. Attempting to install unofficial software on a locked device will lead to an Anti-Rollback error and a possible blink.
2.Firmware methods Redmi S2: which one to choose?
There are three main methods of Redmi S2 firmware, each of which is suitable for different purposes:
| Method | When to use | Pluses | Cons |
|---|---|---|---|
| Through Recovery. | Update the official MIUI without losing data | Simplicity, does not require a PC | Not suitable for custom firmware |
| Fastboot (Mi Flash Tool) | Installation of official firmware in case of failure | Restores the phone after a soft breeze | Requires a PC and an unlocked bootloader |
| Through TWRP (Castom Recovery) | Installation of LineageOS, Pixel Experience, Magisk | Maximum flexibility (root, core, mod) | Hard for beginners, risk of bric |
If you want to just upgrade MIUI to the latest version, Recovery is enough, Fastboot is good for recovering your phone after a crash or installing stock firmware, but custom firmware requires you to install TWRP and unlock the bootloader.
3.Firmware through Recovery: An easy way to update MIUI
This method is suitable for installing official MIUI updates without using a computer, does not require unlocking the bootloader and saves user data (although backup is still recommended).
Step-by-step:
- Download the firmware in.zip format from the official Xiaomi website: 🔗 Download page MIUI Choose a Redmi model S2 (Download Recovery ROM (not Fastboot!).
Move the firmware file to the root directory of the phone’s internal memory (not to folders!).
Recovery
- Turn off the phone.
- Press Volume Up + Power before the Mi logo appears.
- Choose your language (if required).
- From the Recovery menu, select: Install update.zip to System One Confirm installation.
- Once you have finished, select Reboot → Reboot to System.
⚠️ If after firmware, the phone hung on the Xiaomi logo for longer than 10 minutes, reset via Recovery (Wipe Data). → Wipe All Data: This will delete all user data, but often solves the download problem.
What if Recovery doesn’t see the firmware file?
4. Firmware via Fastboot (Mi Flash Tool)
This method is used to completely reinstall the official firmware, for example, if the phone does not turn on or requires a rollback to the stock version.
Required files and tools:
- 🖥️ Official Fastboot Firmware for Redmi S2 (ysl).
- 🔧 Mi Flash Tool (last version).
- 🔌 Xiaomi drivers (set automatically when you connect your phone in Fastboot mode).
- 🔄 Original. USB-cable (important for stable connection).
Step-by-step:
- Unpack the downloaded Fastboot firmware in the folder on the disk C:\ (for example, C:\ysl_fastboot).
- Install the Mi Flash Tool and run the program on behalf of the administrator.
- Turn off your phone and put it in Fastboot mode: Click Volume Down + Power before a bunny with the word Fastboot appears
- Connect your phone to your PC. In the Mi Flash Tool, press Refresh, the device needs to be determined.
- In the field of the path to the firmware, specify a folder with unpacked files.
- Select firmware mode: Clean all - complete cleaning (recommended in case of failures); Clean all and lock - cleaning + lock bootloader (only for official firmware!); Save user data - data storage (not always stable).
Flash
After successful firmware, the phone will restart automatically.
1. Are drivers installed (Android Bootloader Interface should be displayed in Device Manager).
2. whether the original cable is used (cheap cables often do not transmit data to Fastboot).
3. whether the program is running on behalf of the administrator.-->
5. Install custom firmware (LineageOS, Pixel Experience)
If you want to install alternative firmware on the Redmi S2 (like LineageOS 18.1 based on Android 11 or Pixel Experience with pure Android), you will need:
- Unlock the boot loader (see Section 1).
- Install custom Recovery TWRP.
- Sweep the firmware itself and, if necessary, GApps (Google services).
Step 1: Installation of TWRP
Download the latest version of TWRP for Redmi S2 (ysl) from the official website:
🔗 Page TWRP for Redmi S2.
Squeeze Recovery via Fastboot:
fastboot flash recovery twrp-3.7.0_9-0-ysl.img
fastboot boot twrp-3.7.0_9-0-ysl.imgStep 2: Firmware custom OS
- Download firmware (e.g. LineageOS for ysl) and, if necessary, GApps (select arm64 platform, Android 11, pico or nano option).
- Transfer the files to your phone or flash drive.
- In TWRP, run: Wipe → Advanced Wipe → Select Dalvik, Cache, System, Data → Swipe to Wipe Install → Swipe to Confirm Flash → Swipe to Confirm Flash (optional) Install → Select GApps → Swipe to Confirm Flash Reboot → System
How to enter EDL-redmi S2?
7.How to return the official firmware after custom
If you’ve been experimenting with custom firmware but want to go back to the original MIUI, follow this instruction:
- Download Fastboot firmware for your model from the official Xiaomi website.
- Unpack it in a folder on disk C:\.
- Install the Mi Flash Tool and drivers.
- Turn your phone into Fastboot mode (Loudness down + Power).
- In the Mi Flash Tool, select Clean all and lock mode (this will block the bootloader back).
- Switch the device and wait for the automatic reboot.
After this procedure, the phone will return to the stock MIUI, and the bootloader will lock again. If you plan to install custom firmware in the future, do not block the bootloader - just select Clean all mode.
💡
After returning to the official firmware, you may need to re-assign your Mi Account and wait 7 days to unlock the bootloader (if you want to install custom software again).