Set up a 3-2-1 backup that survives deletion and ransomware

Build three copies of your files on two kinds of storage, with one encrypted drive kept offline, so deletions and ransomware can't wipe you out.

This guide turns "my files are in the cloud" into a real backup: three copies of your files, on two kinds of storage, with one copy encrypted and kept unplugged.

Why bother

Cloud sync (iCloud Drive, OneDrive, Google Drive, Dropbox) keeps every device identical. Delete a folder by mistake, or let ransomware encrypt your files, and sync copies the damage everywhere within seconds. Deleted files usually stay in the cloud trash for about 30 days, then they are gone. CISA, the US cybersecurity agency, advises offline, encrypted backups because ransomware looks for backups it can reach and destroys them.

Before you start

Time: 2 to 3 hours for the first full copy, then a short routine once a month.
You need: two external drives, each at least twice the size of the data you want to keep. Use empty drives: setting them up can erase them.
Somewhere else to keep one drive: work, a relative's home, a locker. Somewhere a fire, flood or burglary at home won't reach.
A password manager or a paper notebook for the backup passwords and recovery keys.
Checked on: macOS Ventura 13 and later, Windows 11 and 10, Linux with restic 0.14 or later, iPhone with Finder or the Apple Devices app for Windows, current Android and Samsung Smart Switch.

Steps

1 Make sure your files are really on your computer

Cloud apps often keep files "online only": you see the icon, but the content stays in the cloud, so a backup would save empty placeholders.

OneDrive on Windows: in File Explorer, right-click your OneDrive folder and choose Always keep on this device. On Windows 11 you may need Show more options first. You should see solid green circles with white check marks.
iCloud Drive on Mac: in Finder, click iCloud Drive in the sidebar, select the folders you care about, Control-click and choose Keep Downloaded. Or turn off Optimize Mac Storage under System Settings > [your name] > iCloud > Drive.
iCloud Photos on Mac: in the Photos app, open Photos > Settings > iCloud and choose Download Originals to this Mac.
iCloud on Windows: in the iCloud for Windows app, turn on Photos (with iCloud Photos) and iCloud Drive. In File Explorer, right-click the iCloud Photos and iCloud Drive folders and choose Always keep on this device so the originals download.
Dropbox: right-click your Dropbox folder and choose Make available offline, or set the default to Available offline in Dropbox preferences under Sync.
Google Drive for desktop: click the Drive icon, then Settings > Preferences, click Google Drive (called Folders from Drive in some versions), and under My Drive syncing options choose Mirror files.
Google Photos and other cloud-only data: go to takeout.google.com, select Google Photos, choose Export once and .zip, then Create export. Download the zips within 7 days and put them in a folder on your computer.

You should see the downloads finish and your used disk space go up.

2 Back up your phone to your computer, encrypted

A phone that only syncs to the cloud has the same problem as your laptop. Once the phone backup is on your computer, Step 3 carries it onto your backup drives. iPhone backups skip anything already in iCloud Photos, so those photos reach your computer only through Step 1.

iPhone on a Mac:

Connect the iPhone with a cable, open Finder and select the iPhone in the sidebar.
Under Backups, choose Back up all of the data on your iPhone to this Mac and tick Encrypt local backup.
Set the password, then click Back Up Now.

iPhone on Windows: open the Apple Devices app, select the iPhone, click General, choose Back up all of the data on your iPhone to this computer, tick Encrypt local backup, then Back Up Now. Check it under Manage Backups. The backup is saved in %USERPROFILE%\Apple\MobileSync\Backup, outside your libraries, so Step 3 adds that folder.

You should see the date and time of the latest backup. Encrypted backups also keep Health and Activity data.

Samsung Galaxy: install Smart Switch for PC or Mac, connect the phone by USB, tap Allow on the phone, then click Backup on the computer. When it finishes you should see a summary of what was saved.

Other Android phones: unlock the phone, connect it by USB, tap the Charging this device via USB notification and choose File transfer under Use USB for. Copy the DCIM, Pictures, Download and Documents folders into your computer's Documents folder. Contacts are not in those folders; export them from the Contacts app (Export or Import/export contacts, the wording differs by brand) to a file and copy that too.