What backing up means and why it matters

A backup is a copy of your files stored somewhere other than your computer's main drive. If your hard drive fails, you get a virus, or you accidentally delete something important, a backup lets you restore your work without losing months or years of documents, photos, and settings.

Most people who lose data to hardware failure or ransomware did not have a backup. The cost of recovering data from a failed drive runs into hundreds of dollars. A backup costs nothing if you use free tools, or under $100 a year if you choose a paid service.

You have three realistic options: an external hard drive you plug in yourself, cloud storage that syncs automatically, or both. Each has different trade-offs in speed, convenience, and what happens if your house burns down.

Key Takeaways

  • An external hard drive is the fastest backup method and works offline, but you have to plug it in regularly and it can be lost or damaged in a fire.
  • Cloud backup (like OneDrive, Google Drive, or Backblaze) syncs automatically and protects against fire and theft, but uploads take time on slow internet and you pay a monthly fee for large amounts of storage.
  • The safest approach uses both: an external drive for fast local backups and cloud storage for protection against physical disasters.
  • Windows includes File History (built-in backup tool) and macOS includes Time Machine; both work with an external drive and require no extra software purchase.
  • Start with whichever method fits your budget and habits, then add the second method once the first becomes routine.

External hard drives: fast and under your control

An external hard drive is a portable storage device you plug into your computer via USB. When you connect it, your computer can copy files to it just like copying to a folder. External drives are fast—a full backup of 500 gigabytes can finish in an hour or two, depending on your drive speed and how much data you have.

On Windows, use the built-in File History tool. Open Settings, search for "File History", and click "Add a drive". Select your external drive, then turn on File History. Windows will automatically back up your Documents, Desktop, Downloads, Pictures, and Videos folders every hour when the drive is plugged in. You can also manually back up right now by clicking "Back up now".

On macOS, use Time Machine. Plug in your external drive, open System Settings, click "General", then "Time Machine", and select your drive. Turn on Time Machine. Your Mac will back up automatically every hour. You can also back up when ready by clicking "Back up now" in the Time Machine menu.

The main drawback: you have to remember to plug in the drive regularly. If your drive sits in a drawer for three months, you are not protected during that time. External drives also fail eventually—they typically last three to five years—so plan to replace yours every few years.

Cloud backup: automatic and disaster-proof

Cloud backup means your files are copied to a company's servers over the internet. Once you set it up, the backup happens automatically in the background. If your house floods or burns, your files are still safe thousands of miles away.

OneDrive (Windows) and iCloud Drive (macOS) come built into your operating system. Both offer 5 gigabytes free and sync your Documents and Desktop folders automatically. If you need more space, OneDrive costs $2 per month for 100 gigabytes or $10 per month for 1 terabyte. iCloud+ costs $0.99 per month for 50 gigabytes or $9.99 per month for 2 terabytes.

Google Drive works on both Windows and macOS. It offers 15 gigabytes free and syncs your files automatically. Paid plans start at $1.99 per month for 100 gigabytes.

Backblaze is a dedicated backup service that backs up your entire computer—not just specific folders—for $9 per month or $99 per year. It works on both Windows and macOS. You install the app, turn it on, and it backs up everything in the background. Backblaze is slower than an external drive (uploads happen over the internet), but it protects against every type of disaster.

The main drawback: uploading a large backup takes time. If you have 500 gigabytes to back up and a 10 megabits-per-second internet connection, the first backup can take weeks. After that, only new and changed files upload, which is much faster. Cloud backup also costs money if you need more than the free tier.

Setting up both methods for maximum protection

The best approach combines both: an external drive for speed and convenience, plus cloud backup for disaster protection. You do not need to choose one or the other.

Start with whichever fits your situation. If you have a tight budget and a reliable internet connection, start with cloud backup. If you have a large amount of data and slow internet, start with an external drive. Once the first method becomes routine, add the second.

If you use both, your external drive backs up your computer every hour when plugged in, and your cloud backup syncs automatically in the background. If your drive fails, you restore from cloud. If your cloud account is hacked or locked, you restore from the external drive. If your house burns down, you restore from cloud. This redundancy means you are protected against almost every failure scenario.

What to back up and what to skip

Back up your Documents, Desktop, Downloads, Pictures, Videos, and any folders where you store work or personal files. These are the things that take time to recreate and have real value.

You do not need to back up your Applications folder (you can reinstall programs from the internet) or your operating system (you can reinstall Windows or macOS from Microsoft or Apple). Backing up these takes space and time without adding protection.

If you use cloud backup, be aware that it syncs whatever is in your chosen folders. If you delete a file by accident, it deletes from the cloud backup too after a delay (usually 30 days). External drive backups using File History or Time Machine keep older versions of files, so you can restore a file from weeks ago even if you deleted it recently.

Restoring files when something goes wrong

On Windows with File History, right-click a folder, select "Restore previous versions", and choose the date you want to restore from. You can restore individual files or entire folders.

On macOS with Time Machine, click the Time Machine icon in the menu bar and select "Enter Time Machine". Use the timeline on the right to navigate to the date you want, select the file, and click "Restore".

With cloud backup like OneDrive or Google Drive, log into your account on any computer, navigate to the file, and read it. If you deleted a file, check the Recycle Bin or Trash folder in your cloud account—most services keep deleted files for 30 days before permanently removing them.

If your entire computer fails and you need to restore everything, the process depends on your backup method. With an external drive, you can use Windows Recovery or macOS Recovery to restore your whole system. With cloud backup, you reinstall your operating system, then read and restore your files. This takes longer but works from anywhere.

How often to back up and when to replace your drive

If you use File History or Time Machine with an external drive plugged in regularly, you are backed up hourly. If you use cloud backup, you are backed up continuously as files change. Both are sufficient for most people.

If you do not plug in an external drive for weeks, you are not protected during that time. If you rely only on cloud backup and your internet is down, new files are not backed up until the connection returns. Neither scenario is ideal, which is why using both methods is the safest approach.

External hard drives typically last three to five years before failure becomes likely. If your drive is older than five years, buy a replacement now and set it up before the old one fails. Cloud services like OneDrive, Google Drive, and Backblaze maintain their own redundancy, so you do not need to replace them—you just keep paying the subscription.

Frequently Asked Questions

Can I use the same external drive to back up multiple computers?

Yes. Each computer's backup is stored in a separate folder on the drive. Plug the drive into each computer and set up File History or Time Machine on each one. The drive needs enough space for all backups combined—if you have two computers with 500 gigabytes each, you need at least a 1-terabyte drive.

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

Buy a larger drive and set it up as your new backup destination. Your old drive keeps its backups, so you can still restore from it if needed. Some people keep two external drives and rotate them—one at home and one at a friend's house—for extra protection against fire.

Is cloud backup safe from hackers?

Cloud services like OneDrive, Google Drive, and Backblaze encrypt your files and use security practices that are generally stronger than what most people can set up at home. If your cloud account password is weak or you reuse it elsewhere, a hacker could access your backup. Use a strong, unique password for your cloud account to minimize this risk.

Do I need to back up my phone too?

Yes, but separately. iPhones back up to iCloud automatically. Android phones back up to Google Drive automatically. Both work the same way as computer backup—your data is copied to the cloud and restored if your phone is lost or broken. Check your phone's settings to confirm backup is turned on.

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

You can read all your files before the service closes. Major companies like Microsoft, Google, and Apple are unlikely to disappear, but smaller services do shut down. If you use a smaller cloud backup service, keep an external drive backup as well so you are not dependent on one company.