How to completely clean memory on Xiaomi 9: from cache to system files

Xiaomi 9 (or Mi 9) is still a popular smartphone due to its powerful hardware and up-to-date firmware. However, even 64 or 128 GB of internal memory over time get clogged with unnecessary files: app cache, duplicate photos, remnants of deleted programs and system debris. If your Mi 9 started to slow down, issue notifications about memory shortages or does not update applications, it’s time to do a general cleaning.

In this article, we will discuss 7 working ways to clean memory, from basic (hand-cache removal) to radical (factory reset), and focus on hidden memory reserves that many users miss, such as.thumbnails files or cache system applications like MIUI Gallery.

All the instructions are relevant for Xiaomi 9 based on MIUI 12/13/14 (including global and Chinese versions of firmware).If you have another model of the Mi 9 series (Mi 9 SE, Mi 9 Lite, Mi 9T), the methods will also work – the difference is only in the amount of memory and interface nuances.

1. The analysis of occupied memory: what exactly eats the place?

Before you clean it, you need to figure out which files take up the most space. MIUI has a built-in memory analyzer, but it doesn't always show the full picture. Here's how to get accurate data:

1. Built-in Analyzer: Go to Settings → About Phone → Memory. Here you will see a diagram of the memory distribution by category (applications, images, videos, etc.) Click on any category to see details.
2. Third-party apps: Install Files by Google or SD Maid – they will show hidden cache files, duplicates and debris that are not visible in the standard manager.

Typical memory eaters on Xiaomi 9:

• 📸 Photos and videos: Even after deleting, the gallery can store thumbnails in the.thumbnails folder (weighs up to 1-2 GB).
• 🎮 Games: Genshin Impact or Call of Duty Mobile cache easily reaches 5-10 GB.
• 🗑️ Remnants of Remote Applications: Settings Files and Cache Often Stay in Folders /Android/data and /Android/obb.
• 📥 Downloads: APK-Files, documents and archives are stored in the Download folder.

If you see a System or Other category in the memory analyzer with a volume of more than 10 GB, this is a reason for a deep cleaning (for this in Section 5).

2.Cleaning the app cache: Quick and secure

Cache speeds up applications, but it grows to giant sizes over time. On Xiaomi 9, Facebook, Instagram or TikTok can weigh 500 MB-1 GB each, and you can clean it in two ways:

Method 1: Manual cleaning for individual applications

1. Open Settings → Applications → Application Management.
2. Select an app (such as YouTube) and click Storage.
3. Tap Clear Cache. Don't click Clear Data, it will delete all settings and accounts!

Method 2: Mass cleaning the cache of all applications

1. Go to Settings → About Phone → Memory → Clean.
2. Select the app cache and confirm the action.

After a mass cache clearing, some apps (like Google Maps or Spotify) will take longer to load when you first run – that’s fine.

💡

If after cleaning the cache, the application starts to slow down, restart the smartphone. This will reset the background processes and speed up the work.

3. Delete unnecessary files and duplicates

Even if you regularly delete photos and videos, the Xiaomi 9 still has hidden copies and utility files.

• 📂 folder DCIM/.thumbnails: It stores thumbnails of images, and it doesn't hurt the originals, but it frees up the images. 1–2 GB.
• 🗃️ Download folder: Check for old ones APK, archives.
• 🎵 Music or Ringtones folder: often unneeded audio files are located here.
• 📱 folder Android/obb: contains additional game data (e.g. textures for the PUBG Only delete if you have deleted the game itself.

To find duplicates, use the Files by Google app:

1. Open the app and go to the Cleanup tab.
2. Select Duplicate Files or Unused Applications.
3. Look through the list and remove the unnecessary.

Folder.thumbnails in DCIM|Cash messengers (Telegram, WhatsApp)|Old ones. APK download|Unused screensavers in Ringtones|Remains of remote games in /Android/obb-->

4. Cleaning of garbage with MIUI system tools

MIUI has built-in deep cleaning tools that many users ignore, which remove system debris that you can't see in a standard file manager:

Tool 1: Optimization

1. Open Security. → Optimization.
2. Press Deep Clean and wait for analysis.
3. Delete the found File Residues, Cache Ads and Unnecessary APKs.

Tool 2: "Storage" in the settings

1. Go to Settings → About the phone → Memory.
2. Click Clean and select Garbage Files.
3. Confirm removal.

These tools are removed:

• 🗑️ Remnants of Remote Applications (Folders in the /data/data).
• 📦 Temporary update files (/cache).
• 📋 Logs of the system (/data/log).

⚠️ Note: If after cleaning system tools, the smartphone began to restart or lag, check for important updates in Settings → System update: It is possible that files necessary for firmware to work smoothly have been deleted.

5 Hidden memory reserves: What else can be cleaned?

Even after the cache and debris are removed, the Xiaomi 9 still has hidden files that are not visible in the standard manager, which can be found using a Root Explorer (such as Root Explorer) or ADB-Here's what we need to check:

To access these folders:

1. Connect your smartphone to your PC and use ADB: adb shell su rm -rf /data/log/* rm -rf /cache/*
2. Or install a Root Explorer and manually delete files (root rights required).

⚠️ Note: Delete files in /system or /vendor rootless can cause a device to blink. Don't touch these folders unless you're sure you're doing something!

6. Radical methods: reset to factory settings

If all previous methods did not work, and the Xiaomi 9 still lacks memory, it will be a complete reset (Hard Reset), which will delete all data, including apps, photos and settings, but return the smartphone to a “clean” state.

How to reset:

1. Back up important data (photos, contacts, SMS) through Settings → Additional → Backup or Mi Cloud.
2. Go to Settings → About the phone → Reset settings.
3. Choose to erase all data and confirm the action.
4. After the reboot, set up your smartphone as new.

What the dumping does:

• ✅ Remove all system settings and cache.
• ✅ Frees up space occupied by update remnants and debris MIUI.
• ✅ Corrects errors related to memory fragmentation.

What the dumping doesn't do:

• ❌ Does not increase physical storage (if you have 64 GB, you will have 64 GB left).
• ❌ Does not delete files on SD-map (if it is installed).

💡

Resetting to factory settings is a last resort, so try migrating files to your PC or cloud before you do, and clearing your memory with system tools.

7.How to prevent rapid memory filling in the future?

To keep the memory on Xiaomi 9 from getting clogged up again, follow these tips:

• 📱 Turn off auto-update apps in Google Play: go to Settings → Network settings → Auto Update Apps and Choose Never.
• 📸 Set up automatic cache cleanup in MIUI: Security → Optimization → Autoclean (include and set a schedule).
• ☁️ Use cloud storage: transfer your photo to Google Photos or Mi Cloud and enable the option to Free up space.
• 🎮 Limit the cache of games: In the game settings (such as Genshin Impact) set a cache limit or turn off the download HD-texture.

It is also useful to check the Download folder regularly and delete unnecessary files, and you can use Files by Google with notifications about unused files.

FAQ: Frequent questions about cleaning up Xiaomi 9 memory