Xiaomi’s “Fill Empty Cells” – What is it and How to Use It?

The message “Fill in empty cells” on Xiaomi, Redmi or POCO smartphones often causes confusion among users, and it comes unexpectedly — usually when you connect a device to a PC, try to transfer files or after resetting, many people fear that it is about formatting memory or losing data, but in fact everything is simpler and safer.

This feature is related to optimizing the device’s internal memory, or rather, to the F2FS (Flash-Friendly File System) file system that Xiaomi uses on many models. Empty cells are unused memory blocks that become fragmented over time, and filling them up helps restore the performance of the drive, but only if you do it correctly.

In this article, we’ll look at what actually happens when cells are filled, when they’re needed, and when you can ignore a notification, and you’ll find step-by-step instructions for scenarios ranging from manual optimization to automatic memory error correction.

What are the “empty cells” in Xiaomi memory?

The term “empty cells” (or empty blocks) refers to free clusters in the internal memory of a smartphone. In the F2FS file system, which Xiaomi has been actively implementing since 2018, data is distributed to fixed-sized cells (blocks). Over time, after deleting files, some of these cells become “fragmented” – they are marked as free, but are not physically optimized for a new record.

When the system detects too many of these holes in memory, it suggests that it fill them up — that is, defragment at a low level. It's not the same as formatting! Data is not deleted, but only redistributed to speed up reading / writing.

• 🔍 Not to be confused with cache cleaning: filling cells does not delete temporary files, but optimizes memory structure.
• ⚡ Affects performance: After the procedure, the recording speed can increase by 10-30% (depending on the degree of fragmentation).
• ⚠️ You don’t always have to agree: If your memory is less than 80% full, optimization can be useless.

It’s important to understand that Xiaomi doesn’t always clearly explain this process in the interface, for example, in some versions of MIUI, the notification appears after resetting to factory settings – this is normal, since the system restores the memory structure after cleaning.

When does the notification appear and should it be ignored?

The "Fill in Empty Cells" notification can pop up in different situations, and let's look at the most common cases and whether they need to be addressed:

The notification can be ignored if:

• 📱 Smartphone is stable, there are no lags when writing files.
• 📊 Free memory over 20% (check in Settings) → Memory).
• 🔋 Charge level below 30% – the process may be interrupted.

⚠️ Note: If you see this notification every day, there may be physical errors in your memory. → Memory. → Diagnostics or use the Mi utility PC Suite.

💡

Before filling the cells, close all applications and turn off mobile Internet – this will speed up the process and reduce the risk of failures.

Step-by-step: how to properly fill empty cells

If you want to optimize, follow this instruction, and it takes 5 to 20 minutes depending on the amount of memory and the degree of fragmentation.

Charge your phone to at least 50%|Keep important data (just in case)|Disconnect Wi-Fi and Mobile Network|Close all background applications-->

Step 1. Open the empty cell notification and click "Fill in." If the notification is gone, go to Settings → Memory → Optimization → Fill in the empty cells.

Step 2. Confirm action. The phone will reboot to recovery mode (the Mi logo and progress bar will appear on the screen). Do not turn off the device or remove the battery during the process - this can damage the file system.

Step 3. Once completed, the phone will automatically restart. Check the space available in Settings → Memory – it may decrease slightly (this is normal, as the system reserves some of the memory for service needs).

If the process is suspended during the optimization stage:

1. Wait 30 to 40 minutes (sometimes it takes longer on larger amounts of memory).
2. If nothing changes, force the phone to restart by pressing the power button for 10-15 seconds.
3. After the reboot, check the performance through Settings → Memory → Diagnostics.

Xiaomi models, which most often appear notification

The empty cell optimization feature is active on all devices with the F2FS file system, but most often the notification appears on the following models:

• 📱 Xiaomi Mi 9/9T/10/10T — due to active use F2FS on UFS 2.1.
• 📱 Redmi Note 8 Pro/9 Pro/10 Pro – popular models with a large amount of memory (128/256 GB).
• 📱 POCO F1/F2/F3 — It is often updated, which causes fragmentation.
• 📱 Xiaomi Mi A2/A3 (Android One – Notification may appear here due to stock Android features.

On new flagships (Xiaomi 12/13/14, Redmi K50/K60), the problem is less common due to improved MIUI 13/14 optimization. However, if you actively delete / write large files (for example, 4K video), the notification may appear there.

How to check the file system on your Xiaomi?

1. Install the DevCheck app from Google Play.
2. Open the Storage section.
3. Look at the Filesystem bar – if F2FS is specified, your device supports cell optimization.

⚠️ Attention: On devices with ext4 (Like the old Redmis. 4X/5A) The empty cell notification should not appear. If it is, it could be a software error, and you should contact the service.

What is dangerous incorrect filling of cells?

In most cases, the procedure goes without consequences, but there are risks if you interrupt it or carry out on a discharged phone:

• 💥 File system damage: if you turn off power during optimization, some files may become unavailable.
• 🐢 Slowdown: Incorrect filling can lead to the opposite effect – increased fragmentation.
• 📉 Data loss: In rare cases, photos or documents (usually those that were opened during the process) disappear).

To minimize the risks:

• 🔋 Always optimise with a charge of at least 50%.
• 📴 Turn off your mobile network and Wi-Fi before you start.
• 📂 Backup important data (for example, via Mi Cloud or Google Photos).

If the phone stops turning on after filling the cells or gives an error "No Command" when booting, try:

1. Press Power + Volume up to enter Recovery Mode.
2. Select Wipe & Reset → Wipe All Data (this will erase all data, but restore the functionality).
3. If it doesn’t work, flash the device through the Mi Flash Tool.

💡

Filling empty cells is not a panacea. If the phone is slowing down because of a memory shortage or a weak processor, optimizing the file system will have a temporary effect, and in the long run, only replacing the device or cleaning up the memory will help.

Alternative ways to optimize memory on Xiaomi

If the empty cell notification appears too often, try alternative methods to improve performance:

• 🧹 Cache Cleanup: Go to Settings → Memory. → Clean and delete unnecessary temporary files.
• 🔄 Defragmentation via PC: connect your phone to your computer and use the Mi utility PC Suite (Section Optimization).
• 📦 Transfer of data to SD-card: if your model supports memory expansion, move heavy files (video, music) to the card.
• ⚙️ Factory reset: extreme measure, but effective if fragmentation is critical (don't forget to make a backup!).

For advanced users, there is another way to do this: manual optimization through ADB, which requires skill, but gives you more control.

adb shell


su




f2fs_trim /data

This command runs a TRIM procedure that clears out unused memory blocks. Root rights are required! Without them, the command won't work.

⚠️ Attention: Use ADB And root can lead to a loss of warranty and unstable system operation.

FAQ: Frequent questions about filling empty cells