What Happens When You Enable Windows 11 Compression

What Is 🪟 Windows 11 Compression and How Does It Work?

Windows 11 compression is a built-in tool that shrinks files and folders to save storage space. It finds repeating patterns in the data and replaces them with shorter codes. When you open a compressed file, Windows unpacks it in memory in the background, so you use the file normally with no extra steps.

Think of it like packing a suitcase. Roll your clothes tightly instead of tossing them in flat, and a lot more fits. The clothes are the same when you unpack them, and so are your files.

Two terms often get mixed up here:

• NTFS compressionThis is the per-file and per-folder setting this tutorial covers. It only works on drives formatted as NTFS, which is the default for your Windows 11 system drive. The option will not appear on drives formatted as FAT32 or exFAT, such as many USB sticks and SD cards.
• CompactOSThis is a separate Windows feature that compresses the operating system files themselves. Windows manages it on its own, and you do not need to touch it to follow the steps below.

Compressed files are marked in File Explorer with a small blue double-arrow icon on top of the file or folder icon. That is the easiest way to see what is compressed.

The Main Benefits of Enabling 🪟 Windows 11 Compression

The main benefit is more free space on your drive without buying new hardware. If you compress files you rarely use, you can keep more photos, games and documents on the computer and avoid the cost of an external drive.

• Free Up Valuable Storage SpaceThe biggest benefit is gaining extra gigabytes of room. How much you gain depends on your file types. Text, documents, spreadsheets, logs and some program files shrink the most. You can store more without deleting anything.
• Save MoneyYou do not need to spend money on external hard drives, cloud storage subscriptions, or new internal hardware right away.
• Keep Your Files SafeCompression does not change the content of your files. Your documents, pictures, and programs are exactly the same when you open them. No data is lost.
• Built Right InYou do not need to download third-party software. The tool is part of Windows 11, and it is available in both Home and Pro editions.

The Potential Drawbacks: What Are the Risks?

The main drawback is performance. Your processor has to pack and unpack data every time you save or open a compressed file. On older or budget computers that already struggle with everyday tasks, you may notice the slowdown.

• Slower PerformanceEvery time you open or save a compressed file, the processor must unpack or pack the data. On older or slower computers, this can cause a noticeable drop in speed. On a recent processor you will usually not notice it.
• Not All Files Compress EquallyPlain text documents and spreadsheets shrink significantly. Files that are already compressed, such as JPEG photos, MP3 music files and ZIP archives, will hardly shrink at all. You spend processor effort for very little storage gain.
• Potential Issues with Backups and RecoveryCompressed system files can sometimes complicate advanced system backups or recovery tasks if your computer runs into serious trouble.
• No Encryption on the Same FilesNTFS compression and NTFS file encryption (EFS) cannot be used on the same file. Turning on one turns off the other.

How to Enable Compression on 🪟 Windows 11 (Step-by-Step)

You can apply compression to a single folder, a group of folders, or an entire drive. Start small. Compress one folder of old documents first and see how your computer behaves before you do anything bigger.

Method 1Compressing a Single Folder or File

Compressing a single folder is the safest way to save space, because you only affect the files you choose. You do this from the folder’s properties box in File Explorer.

1. Open File Explorer📁 from your taskbar🖥️, or press the Win and E at the same time. A File Explorer📁 window opens.

   

2. Browse to the folder you want to compress.
3. Right-click the folder and select Properties. You can also select the folder and press Alt+Enter. The Properties window opens on the General tab.
4. On the General tab, near the bottom, click Advanced…. The Advanced Attributes window opens.
5. Check the box next to Compress contents to save disk space. If this box is greyed out, the drive is probably not formatted as NTFS, or Encrypt contents to secure data is already checked. Clear the encryption box first, because the two cannot be used together.
6. Click OK to close the Advanced Attributes window, and then click Apply in the Properties window. A prompt appears asking how to apply the change.
7. Choose Apply changes to this folder, subfolders and files to save the most space, then click OK. Choosing Apply changes to this folder only compresses only files you add to the folder later, not the ones already in it.

Windows compresses the files, which can take a few seconds or a few minutes depending on the folder size. When it finishes, the folder and its files show the blue double-arrow icon. To undo it, repeat the steps and clear the checkbox in step 5. No restart is needed in either direction.

Method 2Compressing an Entire Hard Drive (Admin Privileges Required)

1. Open File Explorer📁 and click This PC in the left pane. Your drives appear on the right.
2. Right-click your main drive, usually labeled Local Disk (C:), and select Properties.
3. Make sure you are on the General tab.
4. Near the bottom of the window, find the checkbox Compress this drive to save disk space. You need administrator privileges to change this setting. If you are signed in with a standard account, Windows asks for an administrator password.
5. Check the box.
6. Click Apply at the bottom right. A confirmation prompt appears.
7. Choose the option to apply the changes to the drive, subfolders and files, then click OK. A progress window appears while Windows works.

Depending on how many files you have, this can take anywhere from a few minutes to a couple of hours. Let your computer finish without turning it off. If Windows reports that some files are in use, choose the option to ignore or skip them. Windows cannot compress files that are currently open, and that is normal.

To undo it, clear the same checkbox and click Apply. Windows expands everything again, which takes about as long as compressing did, so leave the PC running.

Unique Angle: How Compression Impacts Modern Solid-State Drives (SSDs)

Solid-state drives (SSDs) handle compression much better than older mechanical hard drives. They read and write data far faster and have no moving parts, so the extra work of packing and unpacking is usually not noticeable on a modern processor.

Compression can even help on a slow drive or a slow connection. Reading a smaller compressed file takes less time than reading a larger uncompressed one, and that can offset the processor time spent unpacking it. This gain is most likely on mechanical disks and external drives, and the effect on a fast SSD is small either way.

There is one catch regarding SSD wear. Writing data slowly wears out an SSD’s memory cells over a very long period. Compression reduces how much data gets stored, but compressing existing files and rewriting compressed files can add background writes. For a typical home user, the effect on drive life is very small and nothing to worry about.

Expert Tips: When Should You Use Compression (And When to Avoid It)

Compression works best on old documents, tax records and files you rarely open. Avoid it for photos, videos and music, which are already compressed. Compressing only text-heavy, rarely used folders saves the most space and keeps your active files running at full speed.

• Compress Archives and Old Records: Apply compression to folders with old tax documents, school papers, old invoices and archived projects that you rarely open. You save space on active storage without slowing down your daily work.
• Do Not Compress Your Operating System Files Unless Desperate: Compressing the entire C: drive can cause minor hiccups during major Windows feature updates. If you have room, leave the core system files alone and compress only large user data folders.
• Skip Media Folders: Do not bother compressing folders full of movies, MP3 music files, digital camera photos (RAW or JPEG), or downloaded installation packages. These files are already compressed by their creators. Forcing Windows to compress them again wastes processor power and saves almost no space.
• Check Free Space First: Keep some free space on the drive before you start. Compression and decompression both need room to work.

Summary

Windows 11 compression is a built-in tool that shrinks your files and folders to free up storage without new hardware. It may slow down older computers slightly, and it does little for files that are already compressed, such as photos. It works very well on documents and archives. Start with one folder, check how your computer feels, and clear the checkbox if you do not like the result.