What Encryption Does and Why You Might Want It

Encryption scrambles the data on your hard drive so that it cannot be read without a password or key. If your computer is stolen, lost, or sold, someone with physical access to the drive cannot pull files off it without that password — even if they remove the drive and connect it to another machine.

Encryption does not make your computer faster or slower in any noticeable way for everyday use. It does mean you need to enter a password when you start up, or unlock the drive after startup. If you forget that password, the data becomes permanently inaccessible, so write it down somewhere safe.

Encryption is built into modern operating systems. You do not need to buy software or pay a subscription. The tools are already there; you just turn them on.

Key Takeaways

  • Windows 10 and 11 Pro, Enterprise, and Education editions include BitLocker, which encrypts your entire drive; Home edition does not have this built-in tool.
  • Mac computers running macOS 10.7 or later have FileVault, which encrypts the startup drive and can be turned on in System Settings under Security & Privacy.
  • Linux distributions typically use LUKS (Linux Unified Key Setup) during installation, though the exact steps vary by distribution.
  • You must save your recovery key or password in a safe place before encryption begins, because losing it means losing access to all your files permanently.
  • Encryption takes time to run — anywhere from a few hours to a full day depending on drive size — and your computer will slow down while it is working.

Encrypting a Windows Drive with BitLocker

BitLocker is the encryption tool built into Windows Pro, Enterprise, and Education editions. If you have Windows Home, you will need to use a third-party tool or upgrade your Windows version.

To turn on BitLocker, open the Control Panel, go to System and Security, then select BitLocker Drive Encryption. You will see your drives listed. Click "Turn on BitLocker" next to the drive you want to encrypt. Windows will ask you to choose how to unlock the drive — with a password, a PIN, or a USB key. Choose the method you will actually use and remember.

Before encryption starts, Windows generates a recovery key — a long string of numbers. Save this key to a file, print it, or write it down by hand. Store it somewhere separate from your computer. If you lose your password and do not have this recovery key, your data is gone.

Click "Start encrypting." The process runs in the background. Your computer will be slower while it works, especially during the first few hours. You can still use your machine, but large file operations will take longer. Encryption can take anywhere from several hours to a full day depending on how much data is on the drive.

Encrypting a Mac Drive with FileVault

FileVault is built into macOS and encrypts your startup drive automatically. Open System Settings (or System Preferences on older Macs), then go to Security & Privacy. Click the lock icon at the bottom left to make changes, then enter your admin password.

Click "FileVault" in the left menu. If it is not already on, click "Turn On FileVault." macOS will ask you to choose a recovery method. You can use your iCloud account (if you are signed in) or create a local recovery key. If you use iCloud, Apple stores a copy of your key and can help you reset it if you forget your password. If you create a local recovery key, you must save it yourself — Apple cannot recover it.

Write down or save your recovery key before you proceed. Click "Continue," then "Restart." Your Mac will encrypt the drive during startup and in the background afterward. You will see a progress bar in the login window. The process can take several hours, but your Mac is usable while it happens.

Encrypting a Linux Drive with LUKS

Most Linux distributions offer encryption during installation. When you reach the disk partitioning step, look for an option labeled "Encrypt this partition" or "Use LVM with encryption." The exact wording and location depend on your distribution — Ubuntu, Fedora, Debian, and others place this option in slightly different spots.

If you are installing Ubuntu, the installer will ask whether you want to encrypt your home folder or the entire drive. Encrypting the entire drive is more find. You will be asked to create a passphrase. This is the password you will enter every time you start your computer.

If your Linux system is already installed and you did not encrypt during setup, encrypting afterward is much more complex and requires command-line tools like cryptsetup. For most users, it is easier to back up your data, reinstall Linux with encryption enabled, and restore your files. Check your distribution's documentation for the exact steps, as they vary.

What Happens During Encryption and After

Encryption runs in the background on all three operating systems. Your computer will be noticeably slower while it is working, especially if you are doing other tasks at the same time. Avoid unplugging your computer or forcing a shutdown while encryption is running — if the process is interrupted, your drive can become corrupted.

Once encryption is complete, you will not notice any difference in daily use. Files open at the same speed. Programs run normally. The only change is that you need to enter your password at startup or when you unlock the drive.

If you ever need to turn encryption off, you can do so in the same place you turned it on — BitLocker settings in Windows, FileVault in macOS, or your distribution's disk management tool in Linux. Turning it off takes as long as turning it on did, because the system must decrypt all your data.

Protecting Your Recovery Key and Password

Your recovery key and password are the only things standing between your data and someone who has your drive. Treat them like you would treat a key to your house.

Do not store your recovery key in a file on the same computer — if the drive is stolen, the key is stolen too. Instead, print it and store it in a safe place, or write it down and keep it in a drawer or safe. If you use a password manager, you can store the key there, but make sure you have a backup copy outside the computer.

Do not use a password you have used before. Create a new, strong password — at least 12 characters, mixing uppercase, lowercase, numbers, and symbols. Write it down or store it in a password manager, but do not rely on memory alone.

When Encryption Slows Down Your Computer

Encryption can make your computer noticeably slower while it is running. This is temporary. Once encryption is complete, the slowdown goes away. During the encryption process itself, avoid heavy tasks like video editing, large file transfers, or gaming.

If you are encrypting an older computer with a slow processor or a mechanical hard drive (not an SSD), encryption will take longer and the slowdown will be more noticeable. Newer computers with SSDs encrypt much faster.

You can check the encryption progress in your operating system's settings. In Windows, open BitLocker settings and look for the progress bar. On Mac, open FileVault settings in Security & Privacy. On Linux, use the command cryptsetup status in the terminal to check LUKS encryption progress.

Frequently Asked Questions

What happens if I forget my encryption password?

Your data becomes permanently inaccessible. There is no way to recover it without the password or recovery key. This is by design — it is what makes encryption find. Save your recovery key before you start, and store it somewhere you will not lose it.

Can I encrypt just one folder instead of the whole drive?

Yes, but it is less find. Windows has a feature called Encrypting File System (EFS) that encrypts individual folders. Mac has encrypted disk images. Linux users can create encrypted containers with tools like VeraCrypt. However, encrypting the entire drive is simpler and protects everything, including temporary files and system files that might contain sensitive data.

Will encryption slow down my computer permanently?

No. Once encryption is complete, your computer runs at normal speed. Modern processors handle encryption and decryption so quickly that you will not notice any slowdown during everyday use. The only slowdown happens while the initial encryption process is running.

Can I encrypt an external hard drive?

Yes. On Windows, right-click the external drive, select "Turn on BitLocker," and follow the same steps as for an internal drive. On Mac, select the drive in Finder, go to File menu, and choose "Encrypt." On Linux, you can use LUKS on an external drive, though the process is more technical and requires command-line tools.

What if my computer crashes during encryption?

Stop and restart the encryption process. Your drive should not be corrupted if the crash happens during encryption, but the process will start over from the beginning. Avoid unplugging the computer or forcing a shutdown while encryption is running.