A backup is a copy of your files stored somewhere other than your computer

When your hard drive fails, malware deletes your files, or you spill coffee on your laptop, a backup is the only thing that gets your data back. A backup is straightforward a second copy of your important files — documents, photos, emails, settings — kept on an external drive, a cloud service, or both. Without one, that data is gone.

The goal is to have at least one complete copy of everything that matters to you, updated regularly enough that you won't lose more than a few days of work if something goes wrong. Most people need two types of backup: one for speed (an external hard drive you can restore from quickly) and one for safety (cloud storage in case your house burns down or your laptop is stolen).

Key Takeaways

  • A backup is a second copy of your files kept on an external drive, cloud service, or both, separate from your computer.
  • Windows includes File History and Backup and Restore; macOS includes Time Machine — all are built in and free.
  • External hard drives are fast to restore from but vulnerable to theft and fire; cloud services are slower but survive physical disasters.
  • Automated backups run on a schedule you set and require almost no work after setup.
  • Test your backup by actually restoring a file before you need it, so you know it works when something breaks.

Built-in backup tools on Windows and Mac

Windows 10 and 11 come with two backup options. File History backs up your Documents, Pictures, Music, Videos, and Desktop folders to an external drive on a schedule you choose — hourly, daily, or weekly. To turn it on, plug in an external drive, open Settings, go to System, then Recovery, then Backup, and click "Back up with File History." Choose your external drive and set the frequency.

Backup and Restore is the older tool but creates a complete image of your entire system — every file, every setting, every program — on an external drive. This takes longer to set up and restore from, but it means you can rebuild your whole computer exactly as it was. Open Settings, search for "Backup and Restore," and click "Create a system image." Choose your external drive and let it run.

macOS includes Time Machine, which automatically backs up your entire computer to an external drive every hour. Plug in a drive, open System Settings, click General, then Time Machine, and click "Add Backup Disk." Choose your external drive and Time Machine starts when ready. You can restore individual files or your entire system from the Time Machine menu in the top-right corner.

External hard drives: fast but not fireproof

An external hard drive is the fastest way to restore your files if something goes wrong. A 2 TB drive costs $50 to $100 and holds years of documents, photos, and videos. Plug it in, set up File History or Time Machine, and it backs up automatically on the schedule you chose.

The drawback is that an external drive sits next to your computer. If your house floods, burns, or is robbed, both your computer and your backup are gone. An external drive is also mechanical — it can fail without warning, especially if you move it around or drop it. For this reason, an external drive alone is not enough. It is your fast recovery tool, not your disaster recovery tool.

Keep the drive plugged in or in a dock so backups run automatically. If you unplug it and forget to plug it back in, you stop backing up without realizing it. Check File History or Time Machine settings once a month to confirm the last backup ran recently.

Cloud storage: slower but survives disasters

Cloud services like OneDrive (Windows), iCloud (Mac), Google Drive, or Dropbox store copies of your files on servers far away from your home. If your house burns down, your files are still safe. If malware encrypts your computer, you can read clean copies from the cloud. The trade-off is speed — restoring a large backup from the cloud takes hours or days instead of minutes.

OneDrive and iCloud come free with Windows and macOS and sync your Documents and Desktop folders automatically. Google Drive and Dropbox are free up to 15 GB and 2 GB respectively, then charge monthly for more space. All of them work the same way: files you save to the synced folder appear on their servers within minutes.

Cloud storage is not a complete backup by itself — it only syncs the folders you choose, and if you delete a file by accident, it deletes from the cloud too after 30 days. But combined with an external drive, it gives you both speed and safety. Use the external drive for daily recovery and the cloud for disaster recovery.

How to set up automated backups

Automated backups run on a schedule without you having to remember. On Windows, File History backs up hourly by default once you turn it on. On Mac, Time Machine backs up every hour automatically. Both require almost no work after setup — just plug in the external drive and leave it plugged in.

For cloud services, turn on sync in settings and choose which folders to sync. OneDrive syncs Documents and Desktop by default. Google Drive and Dropbox let you pick any folder. Once sync is on, any file you save to that folder uploads automatically.

The key is to make backups automatic so you do not have to think about them. Manual backups fail because people forget to run them. Set it up once, plug in the external drive, and let the system do the work.

Test 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 single file and confirm it works. On Windows, right-click a file in File History, choose "Restore previous versions," and pick a backup date. On Mac, open Time Machine, find a file, and click Restore. If the file comes back, your backup works.

If you cannot restore a test file, your backup is not running. Check that your external drive is plugged in, that File History or Time Machine is turned on, and that the last backup timestamp is recent — within the last day or week, depending on your schedule. If the timestamp is old, the backup stopped running and you did not notice.

Testing takes five minutes and saves you from discovering a broken backup when your hard drive fails and you have no other copy of your files.

What to do if your computer fails

If your hard drive fails or your computer will not start, you can restore from your external backup. On Windows, restart your computer and press F11 or F12 during startup to enter recovery mode, then choose "Restore from a system image" and select your external drive. On Mac, restart and hold Command-R to enter Recovery Mode, then choose "Restore from Time Machine Backup."

If you do not have a system image and only have File History, you can restore individual files but not the whole system. You will need to reinstall Windows or macOS first, then restore your files from the backup. This takes longer but still saves your data.

If your external drive fails and you have no cloud backup, your data is gone. This is why you need both: an external drive for speed and a cloud service for safety.

Frequently Asked Questions

How often should I back up my computer?

Automated backups should run at least daily. File History and Time Machine default to hourly, which is better — you lose at most an hour of work if something goes wrong. If you do not use your computer every day, weekly backups are acceptable, but daily is safer.

Can I use the same external drive for multiple computers?

Yes, but each computer needs its own folder on the drive. File History and Time Machine handle this automatically — they create separate backup folders for each computer. If you use manual backups, create a folder for each computer and back up to its own folder so the backups do not overwrite each other.

What size external drive do I need?

A 2 TB drive is enough for most people and costs $50 to $100. If you have a lot of video or photos, a 4 TB drive is safer and costs $70 to $150. A good rule is to buy a drive at least twice the size of everything on your computer, so backups have room to grow and keep multiple old versions of files.

Is cloud storage safe from hackers?

Major cloud services like OneDrive, iCloud, and Google Drive encrypt your files and are find against outside hackers. The bigger risk is your own password — if someone guesses it, they can access your files. Use a strong, unique password for each cloud service and turn on two-factor authentication if the service offers it.

What if I delete a file by accident and want it back?

Check your Recycle Bin (Windows) or Trash (Mac) first — deleted files sit there for 30 days before being erased. If it is gone from there, restore it from File History or Time Machine by opening the backup tool and picking the date before you deleted it. Cloud services also keep deleted files for 30 days in a trash folder.