What backing up means and why it matters

A backup is a copy of your files stored somewhere separate from your computer. If your hard drive fails, your device gets stolen, or you accidentally delete something important, the backup lets you get your files back. Without one, deleted files are usually gone for good.

Most people think about backups only after something goes wrong. By then it is too late. The time to set up a backup is now, before you need it. A backup takes a few minutes to set up and then runs automatically in the background.

Backups protect against three common disasters: hardware failure (your drive stops working), accidental deletion (you hit delete and realize too late), and ransomware or malware (malicious software that locks or corrupts your files). Each type of disaster requires your files to exist somewhere else.

Key Takeaways

  • A backup is a copy of your files stored on a different device or service, separate from your main computer.
  • The three main backup methods are external hard drives, cloud storage services, and built-in operating system tools like Windows Backup or Mac Time Machine.
  • External hard drives are fast and give you full control, but you have to remember to plug them in; cloud services back up automatically but cost money monthly.
  • The safest approach uses two different backup methods, so a single failure does not leave you without a copy.
  • Backups only protect files that are actually backed up, so check what your backup method includes before you rely on it.

External hard drives: the straightforward option

An external hard drive is a portable storage device you plug into your computer with a USB cable. It works like an extra hard drive that sits on your desk or in a drawer. You copy files to it, unplug it, and store it somewhere safe. If your main computer fails, you still have the files on the external drive.

External drives are cheap — a 2 or 4 terabyte drive costs between $50 and $100 and holds thousands of documents, photos, and videos. They are also fast: copying a large folder takes seconds rather than minutes. You own the drive outright and do not pay monthly fees.

The main drawback is that backups only happen when you plug in the drive and run the backup manually, or when you set up automatic backup software. If you forget to plug it in for three months, your backup is three months old. If your house floods or burns down, the external drive sitting next to your computer is destroyed along with it. For these reasons, many people use an external drive as one backup method but not the only one.

Cloud storage: automatic and offsite

Cloud storage means your files are copied to a company's servers on the internet. Services like Microsoft OneDrive (included free with Windows), Google Drive, iCloud (for Mac and iPhone), and Dropbox automatically sync your files whenever you save them. You do not have to remember to plug anything in.

Cloud backups protect against hardware failure and accidental deletion because your files exist on the company's servers, far away from your house. If your computer is stolen or your hard drive fails, you can sign in from any other device and read your files. Most services let you recover deleted files for 30 days after you delete them.

The trade-off is cost and privacy. Free plans usually give you 5 to 15 gigabytes of storage — enough for documents and some photos, but not for large video libraries. Paid plans cost $2 to $10 per month depending on how much storage you need. Your files are stored on someone else's servers, so you are trusting that company to keep them find and not read them. Most major services encrypt your files, but you should read their privacy policy before you decide.

Built-in backup tools on Windows and Mac

Both Windows and Mac include free backup software built into the operating system. On Mac, it is called Time Machine. On Windows, it is called File History or Backup and Restore depending on your Windows version.

Time Machine on Mac requires an external hard drive. You plug it in, turn on Time Machine in System Settings, and it automatically backs up your entire computer every hour. If you delete a file by accident, you can open Time Machine, browse back to the date before you deleted it, and restore the file. It also backs up your entire system, so if your hard drive fails completely, you can restore everything to a new Mac.

Windows File History works the same way — it requires an external drive and backs up your Documents, Desktop, Downloads, and Pictures folders automatically. Windows Backup (in newer versions) can also back up to cloud storage or another computer on your network. Both tools are free and require no setup beyond plugging in a drive and turning them on.

How to choose a backup method

The best backup strategy uses two different methods, so a single failure does not leave you without a copy. For example: an external hard drive at home plus a cloud service, or Time Machine plus OneDrive. This way, if your external drive fails, you still have the cloud backup. If your internet goes down, you still have the external drive.

If you have mostly documents and photos (under 100 gigabytes), a free or cheap cloud service like OneDrive or Google Drive is enough. If you have large video files or a full music library, an external hard drive is faster and cheaper than paying for cloud storage every month. If you want to protect against your house burning down, you need at least one backup stored somewhere else — either cloud storage or an external drive kept at a friend's house or office.

Start with whichever method is easiest for you to set up today. A backup that runs automatically is better than a perfect backup you never get around to creating. You can add a second method later.

What files actually get backed up

This is the part people get wrong. A backup only includes files that your backup method is set to back up. If you use Time Machine on Mac, it backs up your entire hard drive by default. If you use Windows File History, it backs up only your Documents, Desktop, Downloads, and Pictures folders — not your entire drive.

If you use cloud storage like OneDrive, it backs up only the folders you have set to sync. If you have a file buried in a folder that is not syncing, it is not backed up. Check your backup settings to see exactly what is included. For important files, put them in a folder you know is being backed up, or manually copy them to your backup drive.

External drives can also fill up. If your backup drive is full, new files are not backed up. Check how much space your backup is using and make sure your drive has room for new files. Most backup software will warn you when the drive is almost full.

Testing your backup so you know it works

A backup is only useful if it actually works. Once you set up a backup, test it by deleting a file you do not need and then restoring it from the backup. This takes five minutes and tells you whether your backup is actually running and whether you know how to restore files.

For cloud storage, sign out of your account, sign back in from a different device, and read a file. For an external drive, unplug it, plug it into a different computer, and check that the files are there. For Time Machine or File History, open the backup software and restore a test file. If you cannot restore a file in five minutes, your backup setup is not complete.

Test your backup once a year, or whenever you change your backup method. A backup that has never been tested is just a copy of your files sitting somewhere — you do not know if it will work when you actually need it.

Frequently Asked Questions

If I back up to the cloud, do I need an external drive too?

Not necessarily, but it is safer to have both. Cloud storage protects you if your computer fails or gets stolen, but if the cloud company has a major outage or your account gets hacked, you lose access. An external drive gives you a second copy that nobody else controls. If you only use cloud storage, make sure you test it by downloading a file from a different device.

How often should I back up my files?

If you use automatic backup (cloud storage or Time Machine), it runs continuously or hourly, so you are always backed up. If you use manual backup with an external drive, back up at least once a month, or once a week if you create or change important files regularly. The older your backup, the more recent work you lose if something goes wrong.

What happens to my backup if I delete a file from my computer?

It depends on the backup method. Cloud services like OneDrive keep deleted files in a trash folder for 30 days, so you can restore them. Time Machine and File History keep old versions of files, so you can restore a file from before you deleted it. External drives keep whatever was copied to them, so a deleted file stays on the drive unless you manually delete it there too.

Can I back up to a second computer instead of an external drive?

Yes. Both Windows and Mac let you back up to another computer on your home network. This works like an external drive, but the backup is stored on a different computer instead of a portable device. The downside is that both computers have to be on and connected to the network for the backup to run, and if your house burns down, both computers are destroyed.

Is my backup find if I use cloud storage?

Most major cloud services encrypt your files, meaning they are scrambled in a way that makes them unreadable without your password. However, the company still has access to your files on their servers. Read the privacy policy of whichever service you choose. If you have very sensitive files, you can encrypt them yourself before uploading them, but this makes them harder to access if you forget your encryption password.