How to Back Up Your Computer

Before you buy anything, open your computer and list the folders that would end your week if they vanished: family photos, tax documents, the novel, the password database. For most people it is three to five folders, not the whole drive.

Write the list down and note the size of each folder. That number decides the drive you need and the plan you can actually keep, and it stops you from backing up a terabyte of downloaded films while missing the one folder that matters.

Three copies of the data, on two different kinds of media, with one copy kept somewhere else. Your laptop is copy one. An external drive on the shelf is copy two. A cloud backup or a drive at a relative's house is copy three.

The rule exists because every single storage method fails in a different way. A drive dies, a house floods, a cloud account gets locked. Three copies in three places is the smallest arrangement that survives more than one of those at once.

A full backup copies everything every time: simple, slow, and hungry for space. An incremental backup copies what changed since the last run, which is fast enough to do hourly and is what most backup software does by default.

Pick incremental for daily work and keep one full backup, made monthly, that you never overwrite. The full copy is what saves you when a file is corrupted months ago and the incremental chain has faithfully copied the damage.

Add up the folders on your list, then double it. The extra room covers versions, growth, and the fact that drives slow down and fill up. A 2 TB drive for 500 GB of data is a comfortable place to start, and portable drives of that size are inexpensive.

Buy two identical drives rather than one large one: one stays at home, one goes offsite and swaps with it every month. Identical drives mean identical cables and no surprises when one fails.

Exclude the things you can re-download or rebuild: streaming caches, application installers, virtual machine images, and the trash. They inflate the backup, slow every run, and add nothing you would miss.

Do not exclude your email archive, your browser profile, or your password manager database. Those look like application data and are usually the files people most need after a crash.

Use a port on the laptop or desktop, not an unpowered hub. A hub that loses power for a second during a write can leave the backup corrupted, and cheap hubs drop connections when a second device wakes up.

If you must use a hub, use a powered one, and check after the first run that the drive stayed connected for the whole job.

A new drive often arrives formatted for Windows. On a Mac, open Disk Utility and erase it as APFS or Mac OS Extended; on Windows, use NTFS. If you share the drive between both systems, exFAT works but loses some speed and journaling.

Formatting erases the drive, so check the name twice before you click. Name it something obvious like Backup-2026 so you never confuse it with a working drive.

Windows has File History and Backup; macOS has Time Machine. Both are free, both are already installed, and both are good enough for most people. Open the settings, choose the external drive, and switch the schedule on.

Add your important folders explicitly if the tool does not include them by default — on Windows, File History only covers a few locations until you add more.

The first run copies everything and can take hours. Start it in the evening, plug the laptop in, and let it work. Do not close the lid or let the machine sleep — most tools pause and resume, but a paused first backup is the one people forget to finish.

In the morning, check that the tool reports a completed backup and a sensible size. If it says 12 GB when your photos alone are 200 GB, it skipped something.

An unencrypted backup drive is a plain copy of your life that fits in a coat pocket. Turn on encryption in the backup tool — FileVault-style encryption on a Mac, BitLocker or the tool's own option on Windows — and set a long passphrase.

Store that passphrase in your password manager and on a written copy in a drawer. If you lose it, the backup is unreadable forever; there is no recovery.

Open the backup tool, browse to an old version of a document, and restore it to your desktop. Open the file and confirm it is intact. This takes two minutes and is the only real evidence that you have a backup rather than a folder of bytes.

Do this again after any change to the drive, the cable, or the software. A backup you have never restored from is a hope, not a plan.

Pick a cloud service with versioning — Backblaze, iCloud, Google Drive, or OneDrive all work — and point it at the same folders. The first upload will take days on a home connection; let it run in the background and check the progress weekly.

Cloud storage is copy three. It is not a substitute for the local drive, because restoring a terabyte over a home connection is slow, and it is not a substitute for versioning, because sync tools delete the cloud copy when you delete the local one.

Daily incremental backups, hourly if you work on documents all day, and a monthly full copy. Put a recurring reminder in your calendar to open the backup tool and look at the last-run date.

A red icon in the menu bar is the most common way people discover their backup stopped six weeks ago. Reading the log once a month is the whole maintenance routine.

A clone is an exact copy of the whole drive that you can start the computer from. It is not a substitute for versioned backups, but it turns a dead laptop into a twenty-minute swap instead of a two-day rebuild.

If you skip the clone, write the recovery plan instead: which drive, which cable, which account, which password, and what you install first. Keep it somewhere you can read it when the computer will not start.

Drives are consumables. Watch the health reading in your backup tool if it shows one, and replace the drive at the first sign of reallocated sectors, odd noises, or a run that suddenly takes twice as long.

On the first of every month, take the home drive to the office or a relative's house and bring the other one back. That swap is what makes the offsite copy real rather than theoretical.