How to enable developer mode on Xiaomi Redmi Note 9: from unlock to ADB

Xiaomi Redmi Note 9, powered by a MediaTek Helio G85 or Snapdragon 662 processor (depending on version), hides a lot of power under the hood. The developer mode allows you to fine-tune the system, speed up animations, test new MIUI features, and even install custom firmware. But how to activate it without damaging the device? This article will reveal all the nuances from basic activation to working with ADB and unlocking the bootloader.

It's important to understand that going into developer mode on the Redmi Note 9 requires caution. Some actions (such as unlocking OEM Unlock) can lead to a data reset or warranty cancellation. We'll take a detailed look at each step so you can assess the risks and opportunities. Are you ready to unleash the full potential of your smartphone?

Why you need a developer mode on Redmi Note 9

Developer Mode is not just a hidden menu in MIUI, it is a deep customization tool that allows you to access:

🔧 Debugging by USB — mandatory for work with ADB, customization (TWRP) firmware.
⚡ Accelerating animation: reducing the transition time between screens 0.5x Makes the interface visually faster.
📡 Advanced network settings: forced inclusion 4G/5G, network-type (LTE only).
🛠️ Logs and Diagnostics: Enabling Strict Mode to Detect Lags, Recording Bugreport.
🔓 Unlocking the bootloader is the first step to install Global ROM or LineageOS.

For example, if your Redmi Note 9 is slowing down on MIUI 12.5, in Developer mode you can turn off unnecessary background processes through Inactive Apps or limit Background process limit. And for gamers, Force 4x MSAA is available – Forced smoothing in games (but be careful: this increases the load on the GPU!).

⚠️ Attention: Activation OEM Unlock in the developer menu automatically resets all data to Redmi Note 9 when you first unlock the bootloader. Create a backup through Settings → Additionally. → Backup!

How to turn on the developer mode on Xiaomi Redmi Note 9: step-by-step instructions

The activation process is the same for all versions of the Redmi Note 9 (including the Note 9 Pro and Note 9S), but may vary depending on the version of the MIUI.

Open the Settings. → The phone.
Find the line MIUI version and tap it 7 times in a row, after 3-4 clicks, a notification will appear: "You're almost a developer!"
After pressing 7, the system will say, “You’ve become a developer!”. Now a new section will appear in the main Settings menu – Additional → For developers.

If the section does not appear, check:

🔄 Reboot your smartphone – sometimes MIUI It does not display the menu immediately.
🔍 Make sure you are clicking on the Version. MIUI, Not on the device model or Android.
📱 On some firmware (for example, MIUI EU) The path may be: Settings → System system → The phone. → All specifications → Version. MIUI.

Check the version of MIUI (Settings → About the phone)

Backup of important data

Charge your phone at least 50%

Connect to stable Wi-Fi (for downloading ADB drivers)

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After activation, we recommend you to immediately enable debugging via USB:

Go to Settings → Additional → For developers.
Find the USB debugging option and activate it.
In the window that appears, confirm the action by pressing OK.

⚠️ Note: If you connect Redmi Note 9 to your computer for the first time after debugging is enabled, the request "Allow debugging by debugging" will appear on the smartphone screen. USB?". Always check. RSA-key – if you do not recognize the device, cancel the connection!

Top.-5 Useful features of the developer mode for Redmi Note 9

Now that the developer menu is active, let’s break down the most useful settings for the Redmi Note 9. Not all options are safe – some can impair performance or system stability.

Function	Description	Recommendation
Animation of windows / Animation of transitions	Controls the speed of visual effects (by default 1x)	Install 0.5x to speed up the interface
Inactive applications	Limits background activity of selected applications	Useful for battery saving (e.g. Facebook or TikTok)
GPU-acceleration	Enforcement of use GPU rendering 2D-charting	Not recommended – can cause artifacts and overheating
Background processes	Limits the number of people working in the background	Optimal: Standard Limit or Maximum 4 Process
Choice USB-configuration	Changes USB connection mode (charging, file transfer, MIDI, etc.)	For ADB, select File Transfer (MTP) or PTP

Special attention should be paid to the Strict Mode option, which will flash during long-term operations in the main stream, helping to identify lags, which is useful for performance testing, but in everyday use can be annoying.

💡

If after changing the animation settings, the interface began to twitch, return the default values (1x) and restart the phone.

Unlocking the bootloader on Redmi Note 9: risks and instructions

Unlocking the bootloader is a must for installing custom firmware (LineageOS, Pixel Experience) or TWRP Recovery. However, on the Redmi Note 9, this process has nuances:

🔐 Xiaomi links unlock to Mi Account. Without it, it is impossible to unlock the bootloader.
⏳ The process takes up to 720 hours (30 days) of waiting after the account is linked to the device.
📵 Unlocking resets all data on the phone (including internal memory).
🚫 Xiaomi warranty is cancelled (but you can block the bootloader back).

If you are prepared for these consequences, follow the instructions:

Activate Developer Mode (as described above) and enable: OEM Unlock (in the Developer Menu) Debugging over USB

Connect the Redmi Note 9 to your PC and confirm the debugging permission.

Download the Mi Unlock Tool (the official software from Xiaomi) and install it on your PC.

Launch the Mi Unlock Tool, log in to your Mi Account and follow the instructions. The program will show a waiting timer (usually 168-720 hours).

After the timer expires, repeat the procedure - the loader will be unlocked.

What to do if the Mi Unlock Tool shows a "Couldn't unlock" error

1. Check that you are logged in to the same Mi Account that is linked to the phone. 2. Make sure that the phone is on mobile internet or Wi-Fi (the program authenticates the device). 3. Try using another one. USB-4 If the error "This device is locked" means the timer has not expired yet - wait.

Once unlocked, you can flash TWRP through Fastboot:

fastboot flash recovery twrp.img


fastboot boot twrp.img

Working with ADB and Fastboot: The main commands for Redmi Note 9

ADB (Android Debug Bridge) and Fastboot are tools for interacting with the Redmi Note 9 via the command line, which can be used to install APKs, backups, flash system imagery, and even restore bricks.

First set up. ADB-driver:

Download Android SDK Platform Tools (the official package from Google).
Unpack the archive in the C:\platform-tools folder (for example).
Connect the Redmi Note 9 to your PC and allow debugging over USB.
Open the command prompt in the folder with adb.exe (Shift + right mouse button → “Open command window”).

Check the connection of the device:

adb devices

If everything is set up correctly, you will see the serial number of the phone.

Useful commands for Redmi Note 9:

Team team.	Description
adb reboot bootloader	Reboot to Fastboot Mode
fastboot devices	Checking the connection in Fastboot mode
adb pull /sdcard/Download/ file.jpg	Downloading a file from your phone to your PC
adb shell pm list packages	View the list of installed applications
fastboot flash recovery twrp.img	Custom Recovery (TWRP)

Stock MIUI (official)

MIUI EU (no ads)

LineageOS (Pure Android)

Pixel Experience (like the Google Pixel interface)

Another custom firmware

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To create a full backup system through ADB, use:

adb backup -apk -shared -all -f backup.ab

This command saves all applications, settings, and data on the PC to backup.ab.

adb restore backup.ab

⚠️ Attention: Backup through ADB does not include data from some system applications (such as WhatsApp or Telegram!

Installation of TWRP and custom firmware: Step-by-step

Once you unlock the bootloader, you can install TWRP Recovery, a custom recovery that allows you to flash informal firmware, backup and restore the system. Redmi Note 9 (codenamed merlin) is suitable for TWRP version 3.6.2 or later.

Instructions for installing TWRP:

Download the official TWRP image for Redmi Note 9 from twrp.me.
Reboot your phone to Fastboot: Adb Reboot Bootloader
Fly TWRP through the command line: fastboot flash recovery twrp-3.6.2-merlin.img
Immediately after the firmware reboot to TWRP (not in the system!): fastboot boot twrp-3.6.2-merlin.img
In TWRP, run Wipe → Format Data (this will remove encryption and prevent errors).

Now you can stitch custom firmware. Popular options for the Redmi Note 9:

📱 MIUI EU — Official firmware without advertising and Chinese services.
🤖 LineageOS 19 – pure Android 12 with regular updates.
📱 Pixel Experience – firmware with the interface and features of Google Pixel.
⚡ DerpFest - custom firmware with advanced setting.

For firmware via TWRP:

Download. ZIP-Firmware archive and place it on SD-card.
In TWRP, select Install → Specify the path to the file → Swipe to Confirm Flash.
After installation, run Wipe Cache/Dalvik.
Reboot to the system.

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Before you install custom firmware, always check that it is compatible with the code name of your device (merlin for Redmi Note 9). Installing firmware for another model will lead to a "brick"!

Frequent mistakes and their solutions

When working with the developer mode on the Redmi Note 9, users often face typical problems, and here are the most common ways to solve them:

Mistake.	Reason.	Decision
Mi Unlock Tool shows up to 50% and hangs	Xiaomi servers are overloaded or blocked IP	Try it later or use a VPN (like ProtonVPN)
After unlocking the phone does not turn on	Data reset is interrupted or firmware is damaged	Fastboot: Fastboot with the Mi Flash Tool
ADB does not see the device	There are no drivers or USB-debugging unactivated	Install Mi PC Suite drivers or check your debugging settings
Phone temperature rises sharply after changes	On. GPU-acceleration GPU Rendering	Turn off these options in the developer menu and restart the phone
TWRP asks for password when downloading	Data Encryption (FDE) enabled	Run Format Data in TWRP (the data will be deleted!)

If the Redmi Note 9 has stopped booting (called a "brick") after manipulating the firmware, don't panic. In 90% of cases, the device can be restored via Fastboot:

Download the official firmware for your model from the Xiaomi Firmware website.
Unpack the archive and place the file folder in C:\platform-tools.
Connect your phone in Fastboot mode and do:

fastboot flash boot boot.img


fastboot flash recovery recovery.img




fastboot flash system system.img




fastboot erase userdata




fastboot reboot

If these commands don’t help, use the Mi Flash Tool with the Clean All option (delete all data!).

FAQ: Answers to popular questions

Can I turn on the developer mode without resetting data?

Yes, activating the developer mode itself doesn't cause a reset (OEM Unlock) on Redmi Note 9 will definitely reset all data when you first use. → Additionally. → Backup or ADB.

How to turn off the developer mode if it is no longer needed?

To hide the developer menu, go to Settings → Additional → For developers and in the upper right corner, click three dots → Turn off. Alternatively, you can reset your phone to factory settings (Settings → System → Reset), but this will delete all data.

Why does the phone not pass SafetyNet check after unlocking the bootloader?

The unlocked bootloader breaks SafetyNet, Google’s security mechanism that checks system integrity, which may cause Google Pay, Netflix HD or Pokémon GO to fail. Solutions: Install Magisk and activate MagiskHide. Sweep through a custom core with SafetyNet support (such as Perseus for Redmi Note 9). Use alternative payment methods (such as Samsung Pay or NFC bank cards).

Which firmware is better for Redmi Note 9: MIUI EU or LineageOS?

The choice depends on your priorities: MIUI EU: ✅ All Xiaomi features (themes, dual apps, turbo-game mode). ✅ Stable operation of the camera and sensors. ❌ Advertising in system applications (in some regions: ✅ Clean Android without unnecessary apps. ✅ Quick security updates. ❌ Maybe it won't work. IR-blaster NFS (It depends on the assembly. We recommend it for everyday use. MIUI EU, For experiments, LineageOS.

Can I return the warranty after unlocking the bootloader?

Yes, but you need to: Swipe the official firmware through the Mi Flash Tool. Block the bootloader back: fastboot oem lock ⚠️ Attention: locking the bootloader also resets all data! after that, the Xiaomi service center will not be able to determine that the device has unlocked.