The simplest backup is a copy on a separate device
A backup is a second copy of your files stored somewhere other than your computer or phone. The reason you need one is straightforward: devices fail, get stolen, or break. If your only copy of a file lives on one machine, losing that machine means losing the file.
The easiest backup for most people is to plug in an external hard drive or USB stick once a week and copy your important files to it. You do this manually — select the folders you care about, drag them to the external drive, wait for the copy to finish. It takes 10 to 30 minutes depending on how much you have. Then you unplug the drive and store it somewhere safe, ideally not in the same room as your computer (so a fire or theft doesn't take both).
This method works because it requires almost no setup and you control exactly what gets backed up. The trade-off is that you have to remember to do it, and if your computer fails on a Tuesday and you last backed up on Sunday, you lose three days of work.
Key Takeaways
- A backup is a second copy of your files on a separate device, kept in case your main device fails or gets stolen.
- Manual backups to an external drive are simple to set up but only protect files from the moment you last plugged in the drive.
- Automatic backups run on a schedule without you having to remember, and cloud backups keep a copy off-site so a physical disaster doesn't destroy both copies.
- The best backup strategy uses more than one method — for example, an external drive for speed plus cloud storage for off-site protection.
- Test your backup by actually restoring a file from it before you need it, so you know it works when something goes wrong.
Automatic backups run without you having to remember
If manual backups feel like too much work, you can set up automatic backups that run on a schedule. On Windows, the built-in tool is called File History. On Mac, it is Time Machine. Both watch your files and automatically copy new or changed ones to an external drive at regular intervals — usually every hour.
To set up File History on Windows, plug in an external drive, open Settings, go to System, then Advanced Storage Options, then Backup Options, and select "Back up now". Windows will then back up automatically every hour as long as the drive is plugged in. Time Machine on Mac works similarly: plug in a drive, open System Settings, go to General, then Time Machine, and click "Set Up Time Machine".
The advantage is that you do not have to think about it. The disadvantage is that the backup only exists while the external drive is plugged in. If you leave the drive at home and your laptop gets stolen at work, the backup does not help. Also, if a virus or ransomware infects your computer, it can also infect the backup if the drive is plugged in at the time.
Cloud backups keep a copy away from your home or office
A cloud backup stores your files on a company's servers instead of on a drive you own. Services like Backblaze, Carbonite, and IDrive run in the background on your computer and automatically upload new or changed files to their servers. You pay a monthly or yearly fee — usually between $5 and $15 per month for unlimited storage.
The main advantage is that your backup lives somewhere else. If your house burns down or your laptop is stolen, your files are still safe on the company's servers. You can download them from any computer with an internet connection. The main disadvantage is that it depends on your internet connection — if your upload speed is slow, it can take days or weeks to back up a large amount of data the first time.
Cloud backups also mean a company you do not know has access to your files. Most services encrypt your files so the company cannot read them, but you are trusting that encryption to work and that the company does not lose the data. Read the service's privacy policy to understand what happens to your files and how long the company keeps them if you stop paying.
Combine methods for the strongest protection
The most reliable backup strategy uses more than one method. For example: an external drive with automatic backups for speed and convenience, plus a cloud service for off-site protection. This way, if your external drive fails, you still have the cloud backup. If your house burns down, you still have the external drive at your office or a friend's house, plus the cloud backup.
A common pattern is to back up to an external drive weekly and to a cloud service continuously. The external drive is fast — you can restore a large file in minutes. The cloud backup is safe — it survives physical disasters. Together they cover most ways data can be lost.
If you have very little data — just a few important documents — you can skip the cloud service and instead keep two external drives, storing one at home and one at work or with a trusted friend. This is cheaper but requires more discipline to keep both drives up to date.
What files actually need to be backed up
You do not need to back up everything on your computer. Your operating system, programs, and settings can be reinstalled. What you need to back up are the files you created or downloaded: documents, photos, videos, spreadsheets, email, and anything else you would be upset to lose.
On Windows, this usually means your Documents, Pictures, Videos, and Downloads folders, plus your Desktop. On Mac, it is the same folders plus your Library folder if you use Mail or other apps that store data there. If you use cloud services like Google Drive, OneDrive, or Dropbox, files in those folders are already backed up by the service, so you do not need to back them up again — though it does not hurt to include them.
If you are not sure what to back up, start with Documents and Pictures. Those are almost always the files people regret losing. You can add more folders later.
Test your backup before you need it
A backup is only useful if it actually works. Before you rely on it, restore a file from it to make sure the process works. Pick a file you do not need, delete it from your computer, then restore it from your backup. If you can get it back, your backup is working. If you cannot, you have found a problem while you still have time to fix it.
For an external drive backup, this means plugging in the drive, opening the File History or Time Machine interface, finding an old version of a file, and restoring it. For a cloud backup, it means logging into the service's website, finding a file in your backup, and downloading it. For both, write down the steps so you remember how to do it if you actually need to restore something in a panic.
Backing up a phone or tablet
Phones and tablets need backups too. On iPhone and iPad, the built-in backup is iCloud. Go to Settings, tap your name, then iCloud, then iCloud Backup, and turn it on. Your device will back up automatically when plugged in and connected to Wi-Fi. You can also back up to a Mac using Finder or to a Windows computer using iTunes.
On Android, backups go to Google Drive. Go to Settings, tap Google, then Manage Your Google Account, then Storage, then Backup. Turn on backup and choose what to back up — usually contacts, calendar, photos, and app data. The backup runs automatically when your phone is plugged in and connected to Wi-Fi.
For both iPhone and Android, also back up your photos separately using a cloud service like Google Photos, OneDrive, or iCloud Photos. Phone backups can fail or get deleted, and photos are often the files people most regret losing.
Frequently Asked Questions
How often should I back up?
If you use automatic backups, they run on their own schedule — usually hourly for external drives and continuously for cloud services. If you do manual backups, once a week is a reasonable balance between protection and effort. The more often you back up, the less work you lose if something goes wrong, but the more time you spend backing up.
What if I back up to the cloud and the company goes out of business?
Most cloud backup services let you download all your files before they shut down. Read the terms of service to understand what happens to your data if the company closes. As extra protection, keep a local backup on an external drive as well, so you are not dependent on any single service.
Can I back up to a drive I keep in the same room as my computer?
Yes, but it is less safe. If your house burns down or someone steals both devices, you lose both the original and the backup. If you can only afford one external drive, keep it in a different location — at work, a friend's house, or a safe deposit box. If you have two drives, keep one at home and one elsewhere.
Do I need to encrypt my backup?
If your backup contains sensitive information like financial records or passwords, encryption protects it if the drive is stolen. Most cloud backup services encrypt automatically. For external drives, you can encrypt using BitLocker on Windows or FileVault on Mac. Turn on encryption before you start backing up, because encrypting an existing backup takes a long time.
What if I accidentally delete a file and do not notice for months?
Cloud backups usually keep deleted files for 30 to 90 days before removing them permanently. External drive backups with Time Machine or File History keep multiple versions of files going back weeks or months. Check your backup service's documentation to see how long it keeps deleted files, and restore the file before that period ends.