What backing up your computer means and why it matters

Backing up your computer means making a copy of your files and storing that copy somewhere separate from your main hard drive. If your computer fails, gets stolen, or is damaged by malware, you still have your documents, photos, and settings intact on the backup. Without a backup, a single hardware failure or accident can mean losing years of irreplaceable data.

A backup is not the same as syncing files to the cloud or saving a document to a USB drive. A true backup captures your entire system—or at least all the files that matter to you—in one place, and you can restore from it if something goes wrong. Most people need at least one backup, and many benefit from two: one stored at home and one stored off-site.

Key Takeaways

  • A backup is a complete copy of your files stored separately from your computer, so you can restore them if your hard drive fails or your computer is damaged.
  • Windows computers come with a built-in backup tool called File History; Mac computers have Time Machine, which backs up automatically once you connect an external drive.
  • External hard drives are the most common backup storage method and cost between $50 and $150 for sizes that hold most home computers' data.
  • You should back up at least once a month, though weekly or daily backups are better if you create or change files frequently.
  • Keep one backup at home and consider storing a second backup off-site, in case fire, theft, or flood damages your home.

Choosing between local and cloud backup

A local backup is stored on a physical device in your home—usually an external hard drive or a second internal drive. It is fast, you control it completely, and it does not depend on internet speed. The downside is that if your home is damaged by fire or flood, both your computer and backup could be destroyed.

A cloud backup stores your files on a company's servers over the internet. Services like Backblaze, Carbonite, and IDrive charge a monthly or yearly fee (typically $5 to $15 per month) and keep your data safe even if your home is damaged. The downside is that restoring large amounts of data can be slow, and you depend on the company staying in business and keeping your data find.

Most people use both: a local backup for speed and convenience, and a cloud backup for protection against disaster. If you use only one, a local backup is better than nothing, but a cloud backup is the safer choice if you cannot afford both.

Setting up File History on Windows

Windows 10 and Windows 11 include a built-in backup tool called File History. It backs up your Documents, Desktop, Downloads, Pictures, Music, and Videos folders automatically once you connect an external drive.

To set up File History, plug in an external hard drive, then open Settings (press Windows key + I). Go to System, then About, then scroll down and click "Advanced system settings." In the window that opens, click "System protection" on the left, then click "Configure." Select your external drive from the list, choose "Restore system settings and previous versions of files," and click OK. Windows will now back up your files automatically every hour.

You can also access File History directly by typing "File History" into the Windows search box. Click "Restore your files with File History," then click "Advanced settings" to change how often backups happen (the default is hourly) or how long Windows keeps old versions (the default is one year).

Setting up Time Machine on Mac

Mac computers have a built-in backup tool called Time Machine. It backs up your entire computer automatically once you connect an external drive, and it keeps hourly backups for the past 24 hours, daily backups for the past month, and weekly backups for everything older than a month.

To set up Time Machine, plug in an external hard drive formatted for Mac (most new drives come pre-formatted, but if yours does not, open Disk Utility, select the drive, click Erase, and choose Mac OS Extended). A notification will appear asking if you want to use the drive for Time Machine backups—click "Use as Backup Disk." If the notification does not appear, open System Settings, click General, then Time Machine, click "Add Backup Disk," and select your external drive.

Time Machine will begin backing up when ready and will continue automatically whenever the drive is connected. You do not need to do anything else. To restore files, click the Time Machine icon in the menu bar (top right of your screen) and select "Enter Time Machine," then browse to the date you want to restore from.

Choosing and preparing an external hard drive

An external hard drive is the most common backup storage device. A 1 TB (terabyte) drive costs $50 to $80 and holds about 250,000 photos or 500 hours of video. A 2 TB drive costs $80 to $120. Most home computers need 1 TB or 2 TB unless you store large video files or have many years of photos.

Popular brands include Western Digital, Seagate, and LaCie. Buy from a retailer with a return policy in case the drive arrives damaged. When the drive arrives, connect it to your computer with the included USB cable. Your computer will recognize it automatically. If you are using Windows and want to use File History, you do not need to format the drive—Windows will do it for you. If you are using Mac, format the drive as described in the Time Machine section above.

Store the external drive in a cool, dry place away from direct sunlight and heat sources. Do not leave it plugged in all the time—unplug it after each backup to reduce wear and the risk of power surge damage. If you want a backup that is always running, consider a second external drive that stays connected, or use a cloud backup service instead.

How often to back up and what to do if something goes wrong

Back up at least once a month. If you create or change files every day—documents, photos, emails—back up weekly or even daily. The longer the gap between backups, the more recent work you could lose if your computer fails.

If your computer stops working or you lose important files, connect your backup drive and restore from it. On Windows, open File History, click "Restore personal files," browse to the files you want, and click the restore button. On Mac, open Time Machine from the menu bar, browse to the date you want to restore from, and click Restore. If you cannot restore on your own, a computer repair shop can help, though restoration from a backup is usually faster and cheaper than data recovery from a failed drive.

If you use a cloud backup service, log into your account on the service's website and read the files you need. Most services let you restore individual files or your entire computer, depending on what went wrong.

Backing up specific folders or files only

If your computer is very full or your external drive is small, you can back up only the folders that matter most to you instead of everything. On Windows, open File History, click "Advanced settings," and scroll down to "Exclude folders." Click "Add a folder" and select the folders you do not want to back up—for example, your Downloads folder or a folder full of old video files. File History will skip those folders and back up everything else.

On Mac, open System Settings, click General, then Time Machine, click "Options," and click the plus sign to add folders you want to exclude. Time Machine will skip those folders and back up the rest of your computer.

Alternatively, you can manually copy important folders to an external drive using your file manager. This is slower and requires you to remember to do it, but it works if you only have a few folders to protect. Drag your Documents, Photos, or other important folders to the external drive, and repeat this process monthly.

Frequently Asked Questions

How long does a backup take?

The first backup can take several hours, depending on how much data you have and how fast your external drive is. Subsequent backups are much faster because they only copy files that have changed. A weekly backup of a typical computer usually takes 15 to 60 minutes.

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

Yes, but each computer needs its own backup folder on the drive. On Windows, File History will create a separate folder automatically. On Mac, Time Machine will ask you to erase the drive and use it for only that Mac. If you want to back up multiple Macs to one drive, use a third-party backup tool like Carbon Copy Cloner or Duplicator instead.

What if my external drive fails?

External drives fail sometimes, just like internal drives do. This is why many people keep two backups—one local and one cloud-based, or two external drives. If your backup drive fails and you have no other backup, a data recovery service may be able to recover your files, but it is expensive (often $300 to $1,000). A second backup is cheaper insurance.

Do I need to back up if I use cloud storage like Google Drive or OneDrive?

Cloud storage services like Google Drive, OneDrive, and Dropbox sync your files to the cloud, but they are not backups. If you accidentally delete a file, it disappears from the cloud too (though most services keep deleted files in a trash folder for 30 days). A backup protects against hardware failure, malware, and accidental deletion in ways that cloud storage alone does not.

Can I back up to a USB flash drive instead of an external hard drive?

USB flash drives are too small for most computer backups—a typical flash drive holds 32 GB or 64 GB, while most computers have 250 GB or more of data. Flash drives are better for backing up a few important documents or photos. For a full computer backup, use an external hard drive or cloud backup.