What backing up actually does

A backup is a copy of your files stored somewhere separate from your computer. If your hard drive fails, you get hacked, your laptop is stolen, or you accidentally delete something important, you still have that copy. The backup sits on an external drive, a cloud service, or both — somewhere your computer's main storage cannot reach it.

Backups are not the same as syncing. When you use OneDrive or Google Drive to sync a folder, changes on your computer show up in the cloud, but deletions do the same. If you accidentally delete a file and it syncs, the backup copy is gone too. A true backup keeps older versions of files even after you delete them from your computer.

How often you need to back up depends on how much new work you do. If you create documents, photos, or code every day, a backup once a week or once a day makes sense. If you mostly browse and check email, once a month may be enough. The rule is simple: back up often enough that losing everything since your last backup would hurt.

Key Takeaways

  • External hard drives are the cheapest way to back up large amounts of data, and you control when backups happen.
  • Cloud backup services like Backblaze or Carbonite run automatically in the background and protect against theft or fire, but cost money each month.
  • Windows built-in backup (File History) and Mac Time Machine are free and work well if you connect an external drive regularly.
  • The safest approach uses both: an external drive for fast recovery of recent files, plus cloud backup for protection against physical loss.
  • Backup software should run automatically; manual backups are easy to forget and defeat the whole purpose.

Using an external hard drive with Windows File History

Windows includes a free backup tool called File History that works with any external hard drive. Plug in the drive, open Settings, search for "File History", and turn it on. Windows will ask you to select the external drive as the backup location. After that, File History backs up your Documents, Desktop, Downloads, Pictures, Music, and Videos folders automatically every hour.

File History keeps multiple versions of each file, so you can recover a document from last week even if you overwrote it yesterday. Right-click any folder, select "Restore previous versions", and you see a timeline of backups. Click the date you want and File History restores those files.

The catch is that File History only works when the external drive is plugged in. If you back up once a month, you lose a month of work if the drive fails on day 29. For better protection, leave the drive connected most of the time, or plug it in at least weekly. You can also set File History to back up more often: open File History settings, click "Advanced settings", and change the backup frequency from one hour to 10 minutes if you want.

File History does not back up your operating system or programs, only your personal files. If your computer stops working entirely, you cannot restore Windows itself from File History — you would need to reinstall Windows and then restore your files.

Using Time Machine on Mac

Time Machine is Mac's built-in backup tool and works much like Windows File History. Connect an external drive, open System Settings, click General, then Time Machine, and select the drive. Time Machine backs up automatically every hour after that.

To restore files, click the Time Machine icon in the menu bar and browse through a timeline of your backups. Select the date you want and click Restore. Time Machine also lets you restore your entire Mac to an earlier state if something goes seriously wrong, though this takes longer than restoring individual files.

Like File History, Time Machine needs the external drive connected regularly. If you travel frequently or work away from your desk, leaving the drive at home means no backups happen while you are gone. Some people use Time Machine at home and add cloud backup for when they travel.

Cloud backup for automatic protection

Cloud backup services run in the background and upload your files to remote servers. You do not have to plug anything in or remember to start a backup — it happens automatically. If your computer is stolen, your house burns down, or your hard drive fails, your files are still safe on the company's servers.

Popular cloud backup services include Backblaze, Carbonite, and IDrive. Most charge between $7 and $15 per month for unlimited backup of one computer. They all work similarly: install the software, choose which folders to back up, and the service uploads new and changed files in the background. Initial backup can take days or weeks if you have a lot of files, but after that only changes upload.

The main drawback is cost and speed. Recovering a large backup from the cloud takes time — downloading 500 GB over the internet is much slower than copying from an external drive sitting next to you. Some cloud services will mail you a hard drive with your files if you need to recover everything at once, but that takes a week or more.

Cloud backup also depends on your internet connection. If your upload speed is slow (under 5 Mbps), backups run very slowly and may not finish before your computer goes to sleep. Check your upload speed at speedtest.net before signing up.

Combining external drive and cloud backup

The most reliable approach uses both methods. An external drive gives you fast recovery of recent files — if you delete something by accident, you can restore it in minutes. Cloud backup protects against physical loss — if your house floods or your laptop is stolen, your files are still safe.

Set up File History or Time Machine to back up to an external drive weekly or daily, depending on how much you work. Then add a cloud service like Backblaze for continuous protection. The cloud service runs all the time, so you get backup coverage even when the external drive is not connected. If disaster strikes, you can recover recent files from the external drive (fast) or older files from the cloud (slower but still available).

This approach costs money if you choose a paid cloud service, but the cost is low compared to losing important files. If budget is tight, start with an external drive and add cloud backup later.

What to back up and what to skip

Back up your Documents, Desktop, Downloads, Pictures, Music, and Videos folders — these hold your personal files. Also back up any work folders, email archives, or browser bookmarks you care about. Most backup software lets you choose which folders to include, so you do not have to back up everything.

Skip your Applications folder (Windows Program Files or Mac Applications). Backup software can copy it, but you do not need to — you can reinstall programs from their original installers or app stores if your computer fails. Backing up applications wastes space and can cause problems if you restore them to a different computer.

Skip your operating system. Windows and Mac backup tools do not back up the OS by default, and that is fine. If your hard drive fails completely, you reinstall Windows or macOS from a USB drive or recovery partition, then restore your files from backup. This takes longer than restoring a full system image, but it is simpler and more reliable.

Testing your backup before you need it

A backup that has never been tested is not a backup — it is a hope. Before you rely on it, restore a test file to make sure it actually works. Delete a document you do not need, wait a day, then restore it from your backup. If it comes back, your backup is working. If it does not, something is wrong and you need to fix it before a real disaster happens.

Test both your external drive backup and your cloud backup if you use both. For the external drive, unplug it, plug it back in, and restore a file. For cloud backup, open the backup software and use its restore feature. Do this once every few months so you know what to do if you actually need to recover files.

Frequently Asked Questions

How much storage do I need for an external backup drive?

Get a drive at least as large as your computer's hard drive, ideally larger. If your computer has 500 GB of files, a 1 TB (1000 GB) external drive gives you room for backups plus some extra space. Larger drives are cheap — a 2 TB external drive costs $50 to $80 and lasts for years.

Can I back up to a second internal hard drive in the same computer?

Technically yes, but it is not safe. If your computer is stolen or the motherboard fails, both drives are gone. An external drive you can unplug and store elsewhere, or a cloud service on someone else's servers, protects against this. Internal backup is better than nothing, but external or cloud is much better.

What if I run out of space on my backup drive?

Backup software will stop backing up and alert you. Delete old backups you no longer need, or buy a larger drive. Most backup tools let you set how many old versions to keep — if you only need backups from the last three months, you can delete anything older than that to free up space.

Do I need to encrypt my backup?

If your backup contains sensitive information like tax returns, medical records, or financial documents, encryption is a good idea. Most backup software includes encryption options. For an external drive, you can use Windows BitLocker or Mac FileVault to encrypt the entire drive. For cloud backup, the service usually encrypts automatically.

What happens if my cloud backup company goes out of business?

You can download your files before they shut down — companies give customers time to retrieve their data. But this is one reason to use both external drive and cloud backup. If one fails, you still have the other.