Why the Redmi Note 9 is slowing down and what to do about it
Xiaomi Redmi Note 9 with MediaTek Helio G85 processor and 3/4/6 GB of RAM at release in 2020 showed excellent performance in its segment. But after 2-3 years of active use, many owners face slow animations, long downloads of applications and sudden friezes.
Software: cache cache, fragmented memory, MIUI background processes that consume resources aggressively. Hardware: battery wear (at a charge below 20%, the processor automatically reduces the frequency), overheating due to dust in the case. Systemic: outdated firmware, conflicting updates or “curved” security patches from Xiaomi. For example, after upgrading to MIUI 14 based on Android 12, many users complained about the lags when scrolling the desktop — this was a bug optimization MIUI Launcher.
The good news is that 90 percent of the time, you can fix the problem without replacing the iron, and the steps below are from the safest methods (cleaning the cache) to the radical ones (resetting to the factory settings), and the important thing is that if your Redmi Note 9 crashes into a bootloop or crashes into a Fastboot, it's a hardware malfunction, and you can't do without a service center.
1.Cache and garbage cleanup: a quick way to free up memory
The easiest and safest method is to delete temporary files that accumulate in the system. On the Redmi Note 9, the cache can take up to 5-8 GB, even if you have not installed heavy games, especially messaging messengers (Telegram, WhatsApp) and social networks (TikTok, Instagram).
How to clear the cache:
- 📱 Go to Settings. → Annexes → Application management.
- 🔍 Select an app (such as Chrome or Facebook) → Warehouse → Clear the cache.
- 🧹 For mass cleaning: Settings → Memory. → Cleaning up garbage (use the built-in tool) MIUI Optimizer).
- 🗑️ Remove unnecessary files in files → Categories → Multimedia/Documents.
Warning: Do not clear the cache of system applications (for example, com.android.systemui) - this can cause the interface to crash and reboot the smartphone. Also do not delete application data (Clear data) unless you want to lose logins and settings.
Clear the browser cache (Chrome, Mi Browser)
Delete downloaded files from Telegram/WhatsApp
Check the Download folder (downloads)
Clear the cache of Google Play Services
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2. MIUI optimization: disabling unnecessary functions and animations
MIUI is known for its heavyweight interface, with beautiful animations, widgets and background services eating up to 15-20% of the processor even in standby mode, and turning off the excess effects can give you up to 30% speed gain when you scroll through menus and launch apps.
What can be turned off:
- 🎨 Animations: Go to Settings → About the phone, tap 7 times on the version MIUI, To activate Developer Mode. Then to Settings. → Additionally. → For developers, set: The scale of the window animation → No animations The scale of transition animation → Without animation Duration of animation → 0.5x
- 📊 Background Activity: In the same developer settings, turn off Background Process Limitation and set a limit of 2 processes.
- 🔄 Auto Update: Settings → Annexes → Auto-update → Choose Only over Wi-Fi or Never.
- 📱 Secondary Space: If you don’t use it, delete it in Settings → Memory. → Secondary space.
⚠️ Warning: Disabling animations will make the interface less smooth visually, but will speed up the system's response. If artifacts appear after the changes (for example, a black screen when folding applications), return the settings to the factory settings.
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To quickly reboot MIUI Launcher (if it brakes the desktop), hold your finger in the free screen space → Home screen settings → More → Restart.
3. Developer settings: hidden settings for acceleration
Redmi Note 9 has more than 50 parameters that you can customize to improve performance.
| Parameter | Recommended value | The effect |
|---|---|---|
| Not to keep up the action | Included. | Reduces memory load when switching between applications |
| GPU-acceleration | Included (if supported) | Improves performance in games and 3D-annexes |
| Background process for the annex | 2 process | Reduces RAM consumption by background tasks |
| USB debugging | Disabled (if not used) | Prevents conflicts with ADB-team |
| Aggressive closure of applications | Included. | Forced to close unused applications |
How to activate the developer mode:
- Go to Settings → About Phone → MIUI version.
- Slap it 7 times in a row (the notification will appear "You became a developer").
- Back to Settings → Additionally. → For developers.
⚠️ Warning: Do not turn on the "keep screen on" setting, which will quickly drain the battery. Also avoid changing the "may cause layout issues in apps).
4. Battery Optimization: Why the discharge slows down the smartphone
Few people know, but the Redmi Note 9 automatically reduces the performance of the processor at a charge level below 15-20%, this is done to save energy, but leads to noticeable lags. In addition, a worn battery (capacity below 80%) can cause accidental reboots and friezes due to unstable voltage.
How to check the status of the battery:
- Enter the dialer code ##4636##.
- Select Battery Information.
- If you look at the health setting, if it's below 85%, the battery needs to be replaced.
Optimization tips:
- 🔋 Turn off battery optimization for critical applications: Settings → Battery. → Optimizing the battery → select the application → No restrictions.
- ⚡ Use the original power supply unit (5V/2A or 9V/2A). Cheap charging can cause voltage drawdowns.
- 🔄 If the phone is slowing down 10-30% charge, turn on the performance mode in Settings → Battery. → Regimes.
- 🛑 Avoid full discharge (below 5%) – this accelerates battery degradation.
What happens if you turn off battery optimization for all applications?
5. Reset to factory settings: when it really needs to
If all previous methods failed, the last chance before visiting the service center is hard reset. This will delete all data, but return the smartphone to a "clean" state. On the Redmi Note 9, the reset solves problems with:
- 🐢 Slowdown after update MIUI.
- 🔄 Cyclical reboots (bootloop).
- 📱 Hanging on the Xiaomi or Redmi logo.
- 🚫 Errors like "Com.android.systemui process stopped".
How to reset:
- Create a backup: Settings → About Phone → Backup.
- Go to Settings → About the phone → Reset settings.
- Choose to erase all data and confirm.
- After restarting, set your phone as new.
⚠️ Note: if the phone again brakes after reset, the problem may be in the hardware (for example, a faulty flash memory eMMC 5.1.
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The factory reset deletes all data, including photos, contacts and messages, and if you don't back up, it won't be possible to recover the information.
6 Radical methods: firmware and iron replacement
If the software methods didn't work, there are two options: firmware or hardware upgrades, the first one is suitable for advanced users, the second one is if you are willing to invest in repairs.
Firmware:
- 📲 Install custom software (like LineageOS or Pixel Experience) – this will remove unnecessary Xiaomi services and speed up the work.
- 🔄 Reverse to the old version MIUI (for example, MIUI 14 on MIUI 12.5) if the lags started after the update.
- 🛠️ Use it. ADB to remove system applications (requires unlocking the bootloader).
Hardware upgrade:
- 🔋 Replacement of the battery (cost) ~1500-2500 ₽). New battery will eliminate voltage drawdowns and accidental reboots.
- 💾 Replacement of eMMC flash memory with UFS 2.1 (It is expensive, but it increases the speed of reading / writing in the 2-3 once).
- 🧊 Dust cleaning and heat paste replacement (relevant if the phone overheats and trottlites).
⚠️ Warning: Firmware that is unofficial will void the warranty and may result in a device being "bricked" (completely inoperable.
7.Alternative methods: cloud solutions and external devices
If your Redmi Note 9 is slowing down due to memory shortages, but you don’t want to delete files, consider:
- ☁️ Cloud storage: transfer photos and documents to Google Drive, Mi Cloud or Yandex Disk. For example, 15GB in Google Photos is free.
- 💾 Memory Card: Install a MicroSD Class A2 (For example, SanDisk Ultra and transfer applications to it through Settings → Annexes → Move it to SD.
- 🖥️ Desktop mode: connect the phone to the monitor through USB-C → HDMI Adapter and use as a PC (DeX function in the computer) MIUI limited, but the basic tasks can be performed).
- 🎮 Cloud Gaming: Play Heavy Games via Xbox Cloud Gaming or GeForce NOW, processor-free.
⚠️ Note: not all applications support microSD portability, for example, WhatsApp and Telegram will not allow you to move the cache to an external drive.