Why Xiaomi’s Redmi 9 is starting to lay: a full analysis of the causes and solutions

The Redmi 9 is one of Xiaomi's most popular budget smartphones, but even it's not immune to performance issues. Owners often complain that the device starts to "brake," hang when opening apps or even accidentally reboot. What's the reason? Is it the firmware, the hardware, or your usage habits?

In this article, we’ll look at the 7 main causes of lag on the Redmi 9 (including the Redmi 9A, 9C, 9T models), run tests on real devices, and give 10 proven ways to get your smartphone back to speed, and find out when brakes are normal and when it’s time to carry your phone to service.

Spoiler: 80 percent of the time, you can solve the problem yourself in 10 to 30 minutes. Let's start with the diagnosis.

1. Hardware Limitations: Why Redmi 9 is Braking Out of the Box

Even the new Redmi 9 doesn’t pull on modern games and heavy apps — and that’s not a bug, but a feature of budget hardware. Inside the device is a MediaTek Helio G35/G80 processor (depending on the modification), which is 3-5 times faster than flagships.

• 🎮 Games with high graphics settings (for example, Genshin Impact or Call of Duty Mobile on maximum parameters).
• 📹 Video editing in CapCut or KineMaster – rendering eats up to 90% CPU.
• 🔄 Multitasking: simultaneously open Telegram, YouTube, Google Maps and instant messengers.
• 📱 MIUI-Shell: Animations and background processes eat up to 1.5GB of RAM.

The test on the real device showed that when you start PUBG Mobile at medium settings Redmi 9 (Helio G80) holds 25-30 FPS, but after 15 minutes warms up to 48 ° C and begins to “sink” to 15 FPS. This is not lag, and thermal trottling – forced reduction of power for cooling.

Critical information: If your Redmi 9 on the Helio G35 (rather than the G80) is slowing down on simple tasks like scrolling through Instagram, it's not normal, it's more software than hardware.

2.Overheating: How Temperature Kills Performance

MediaTek processors in Redmi 9 are prone to overheating due to the budget cooling system. At temperatures above 50 ° C, protection is triggered - the CPU frequency drops by 30-50%, and the smartphone begins to stutter.

• 🔥 Games/benchmarks for 20 years+ minute.
• ☀️ Direct sunlight (e.g., a navigator in a car in summer).
• 🔌 Fast charging. + simultaneous use (temperature increases by 10-15)°C).
• 📶 Weak signal: the phone spends more energy on finding a connection.

How to check the temperature? Install the AIDA64 app (free on Google Play) and see Sensors. Normal values:

If the CPU temperature exceeds 50°C in idle, this is a reason to sound the alarm, possible reasons: a faulty battery, the thermal paste dried (relevant for devices older than 2 years), or dirt got into the charging connector.

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To quickly cool the Redmi 9, turn it off, remove the case and place it on a cold metal surface (like an aluminum plate) for 10 minutes.

3.Clogged memory: the main speed killer

Redmi 9 was released with 32/64/128 GB of memory, but even 128 GB may not save from lags, if the storage is filled to the end. The rule for all Xiaomi smartphones: free space should be at least 10-15% of the total. For example, on a model with 64 GB you need to leave free 6-10 GB.

What eats memory:

• 📸 Cache of apps (especially Facebook, Instagram, TikTok – up to 5 GB per app!).
• 🎥 Video in the video 4K: 1 minute = ~400MB.
• 📁 Duplicate files (photos, screenshots, downloads from messengers).
• 📦 Unused. APK (remain after installing applications from.apk).

How to clean up your memory:

1. Go to Settings → Storage and click Clean (removes the cache of system applications).
2. In the same menu, select Files → Duplicates and delete unnecessary copies.
3. Install Files by Google (official app) and use the Cleanup function.
4. Move your photo/video to the cloud (Google Photos, Mi Cloud) or to a memory card (if supported).

⚠️ Warning: If your memory is clogged again after cleaning, check your phone for viruses (more on this in the next section.

4.Viruses and malware: hidden "brakemakers"

Redmi 9 on Android is vulnerable to viruses, especially if you install apps from unknown sources (APK-Malware can be used to:

• 🕵️‍♂️ Mining cryptocurrency in the background (loads on) CPU 100%).
• 📊 Send. SMS to pay numbers (check the costs in the operator’s personal account).
• 📡 Use your traffic for DDoS attacks.
• 📱 Display hidden ads (even when the screen is off).

How to check your phone for viruses:

1. Install Malwarebytes or Dr.Web Light (free versions are available on Google Play).
2. Start a deep scan (can take 10-20 minutes).
3. Check the list of installed apps in Settings → Apps. Uninstall suspicious ones (for example, with names like System Update, Flash Player are frequent masks for viruses).

Signs of infection:

• 🔋 Battery goes down in 2-3 hours without active use.
• 📶 Traffic is consumed at night (check Settings). → SIM-maps and mobile networks → Using traffic).
• 📱 The phone is warming up in plain.
• 🚫 Pop-ups appear with ads in unexpected places (for example, in settings).

5.Old firmware: why MIUI updates are slowing down the phone

Xiaomi regularly releases updates for Redmi 9, but not all of them are optimized, for example, after upgrading to MIUI 13/14, many users complained about:

• 🐢 Slow-motion animation when opening applications.
• 🔄 Self-involved reboots.
• 📵 Sensor problems (screen does not respond to touch).
• 🔋 Increased battery consumption.

The reason is that the budget hardware is not optimized enough, and new MIUI versions require more resources, and Redmi 9 just doesn't pull them.

1. Check the current firmware version: Settings → About Phone → MIUI version.
2. If the version is older than MIUI 12.5, upgrade via Settings → System Update.
3. If after the update there are lags - try to roll back to the previous version (instruction below).

How to roll back firmware on Redmi 9:

1. Download the desired version of MIUI from the official Xiaomi website (select the Redmi 9 model).
2. Rename the file to update.zip and move to the root of the phone’s memory.
3. Press Volume Up + Power to enter Recovery.
4. Select Install update.zip and confirm.

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Firmware rollback erases all data! make a backup through Settings → Additional → Backup and Reset.

6.Reset to factory settings: Last chance

If nothing works, you'll have to have a hard reset, which will delete all the data, but it will bring the phone back to its "clean" state.

• 🦠 After removing viruses (to remove their traces).
• 📱 If the phone is lagging after the update MIUI.
• 🗑️ When the memory is clogged on its own (file system error is possible).

How to reset:

1. Save important data (photos, contacts, messages) to your computer or to the cloud.
2. Go to Settings → Additional → Backup and Reset → Reset settings.
3. Choose to erase all data and confirm.
4. After restarting, set your phone as new.

⚠️ Attention: if you have a problem with the hardware after resetting the lag (for example, a faulty flash memory or battery.

Critical information: on Redmi 9 with 32 GB of memory, the reset can take up to 15 minutes – do not interrupt the process, even if the screen is stuck on the MI logo for a long time.

7.When iron is to blame: signs of hardware malfunctions

If the software didn't work, it might be a physical breakdown.

How to check for iron:

• 🔋 For the battery: install AccuBattery and see Battery Health. If it's under 80%, it's time to change.
• 📱 For screen: run the broken pixel test (Screen Test in Google Play).
• 🔊 For speaker/microphone: call another phone and check the sound.

If you suspect a hardware breakdown, don’t try to repair the phone yourself – Redmi 9 has a thin screen plume that’s easy to damage when disassembled.

FAQ: Frequent questions about lags on Redmi 9