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, you get hacked, your device is stolen, or malware wipes your data, a backup lets you restore everything — your photos, documents, email, and settings — to a new or repaired machine. Without one, that data is often gone for good.
Most people wait until something breaks to think about backups. By then it is too late. The time to set one up is now, while your computer still works. A good backup takes a few hours to set up and then runs on its own.
Key Takeaways
- The safest backup strategy uses two locations: one external drive at home and one cloud service, so a single failure does not wipe out both copies.
- Windows includes a built-in backup tool called File History; Mac includes Time Machine — both are free and require only an external hard drive.
- Cloud backup services like OneDrive, Google Drive, or Backblaze run automatically in the background and protect against theft and hardware failure at the same location.
- An external hard drive should be disconnected and stored away from your computer most of the time, so a power surge or theft does not destroy both the original and the backup.
- Test your backup by actually restoring a file from it before you need it in an emergency.
Local backup with an external hard drive
An external hard drive is a portable storage device you plug into your computer via USB. It holds a complete copy of your files and can restore them quickly if something goes wrong. A 1 or 2 terabyte drive costs between $50 and $100 and holds years of photos, documents, and videos for most people.
On Windows, use File History. Plug in the external drive, open Settings, search for "File History," and select it. Click "Add a drive" and choose your external drive. Windows will then back up your Documents, Desktop, Downloads, Pictures, Music, and Videos folders automatically every hour. You can change the frequency in the same menu.
On Mac, use Time Machine. Plug in the external drive, open System Settings, click "General," then "Time Machine," and select "Add Backup Disk." Choose your external drive. Time Machine will back up your entire computer automatically every hour and keep older versions so you can restore a file from any point in the past.
After the first backup completes (which can take several hours depending on how much data you have), disconnect the drive and store it somewhere safe — a closet, a drawer, or a different room. This way, if your computer is stolen or damaged, the backup is not sitting right next to it. Reconnect it once a week or once a month to let it update.
Cloud backup for automatic protection
Cloud backup stores copies of your files on servers owned by a company, accessible from anywhere you have internet. Unlike an external drive, cloud backup runs automatically without you plugging anything in, and it protects against theft, fire, and hardware failure at your location.
OneDrive (Windows) and iCloud Drive (Mac) come built into your operating system. Both offer 5 GB free and sync your files automatically. If you use more than 5 GB, they charge a monthly fee — typically $2 to $10 depending on storage size. These services sync files you choose, so they work best for documents and photos but may not back up your entire system.
Google Drive works on any computer and offers 15 GB free. Like OneDrive and iCloud, it syncs files you select rather than your whole system. Backblaze is a dedicated backup service that copies your entire computer automatically for about $7 per month. It runs in the background and keeps older versions of files so you can restore from any date.
The advantage of cloud backup is that you never have to think about it — it runs while you work. The disadvantage is that it costs money for large amounts of storage, and restoring a full computer can take a long time if your internet is slow. Most people use cloud backup for important files and an external drive for a complete system backup.
Combining local and cloud for maximum safety
The best backup strategy uses both an external drive and a cloud service. This way, if your external drive fails, you still have the cloud copy. If your cloud account is hacked or deleted, you still have the external drive. If your house burns down, the cloud copy survives. If your internet goes out, the external drive is still there.
A straightforward setup: use File History or Time Machine with an external drive for a complete system backup, and use OneDrive, Google Drive, or iCloud for your most important files — photos, documents, tax records. Store the external drive away from your computer. Let the cloud service run automatically. Check both once a month to make sure they are working.
You do not need to pay for multiple services. If you already use OneDrive or Google Drive, add an external drive. If you prefer a dedicated cloud backup, Backblaze alone covers your entire system. The key is having two separate copies in two separate locations.
What to back up and what you can skip
Back up everything in your Documents, Desktop, Downloads, Pictures, Music, and Videos folders. Back up your email if you use a desktop email client like Outlook or Mail. Back up any files you created or downloaded. Most backup tools do this automatically.
You do not need to back up your operating system or installed programs — you can reinstall Windows or macOS from a recovery disk or read, and you can reinstall programs from the App Store or the publisher's website. Backing up the entire system is fine and actually simpler, but it is not necessary.
If you use cloud services like Gmail, OneDrive, or Google Photos, those files are already backed up by the company that runs them. You do not need to back them up again unless you want a local copy for faster access.
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 single file from it to make sure it actually works. This takes 10 minutes and can save you from a nasty surprise later.
On Windows with File History, right-click a file in your Documents or Pictures folder, select "Restore previous versions," and restore an old version to a test folder. On Mac with Time Machine, open a folder, click the Time Machine icon in the menu bar, and restore an old version of a file. If the file appears and opens correctly, your backup is working.
If you use cloud backup, read a file from the cloud service to your computer and open it. If you use Backblaze, log into your account online and read a file from the backup. All of these should work smoothly. If they do not, contact the service's support before you actually need the backup.
What to do if your computer fails
If your computer stops working, crashes, or gets infected, do not panic. If you have a backup, your data is safe. Here is what to do:
- If the computer still turns on, try to restore from your backup using File History or Time Machine before doing anything else.
- If the computer does not turn on or the drive is damaged, you can restore to a new computer or a repaired one once it is ready. Plug in your external drive or log into your cloud account and restore your files.
- If you have both an external drive and cloud backup, start with whichever is fastest or most convenient. Both should have the same files.
- If your backup is also corrupted or lost, a data recovery service may be able to retrieve files from your original drive, but this is expensive ($300 to $3,000) and not always successful. This is why having two backups matters.
Frequently Asked Questions
How often should I back up my computer?
If you use File History, Time Machine, or a cloud service set to automatic sync, you do not need to do anything — they back up continuously or on a schedule. If you use an external drive manually, back it up at least once a month, or once a week if you create or change files frequently. The more often you back up, the less data you lose if something goes wrong.
Can I use the same external drive to back up two computers?
Yes, but it is more complicated. File History and Time Machine can each manage their own backup on the same drive, but you need to make sure they do not overwrite each other. It is simpler to use one drive per computer, or to use cloud backup for one computer and an external drive for the other.
What if I run out of space on my external drive?
Buy a larger drive. A 2 or 4 terabyte drive costs $60 to $120 and will hold backups for years. You can also delete old backups from File History or Time Machine settings to free up space, but keeping older versions is useful if you need to restore a file from months ago.
Is cloud backup safe from hackers?
Major cloud services like OneDrive, Google Drive, and Backblaze encrypt your files and protect them with security measures. Your files are safer in the cloud than on a computer sitting on your desk. However, if someone gets your password, they can access your cloud files. Use a strong, unique password and enable two-factor authentication if the service offers it.
Do I need to back up my phone too?
Yes, but phones have built-in backup. iPhone backs up to iCloud automatically if you are signed in. Android backs up to Google Drive. These happen in the background, so you do not need to do anything. If you want a local copy, you can plug your phone into your computer and use iTunes (Mac) or a third-party tool (Windows).