Cloud storage and file synchronisation: OneDrive, Dropbox and co.

In short: Cloud storage keeps files on servers on the internet and syncs them between your devices; it does not replace a real backup, though.

In more detail: Services such as OneDrive, Google Drive, iCloud, Dropbox and Nextcloud store files online. A program on the computer synchronises a folder: what you change there appears on other devices and in the browser.

In Depth

Advantages

• Access from anywhere and on several devices.
• Sharing via link, working together on documents.
• Version history and recycle bin to restore changes.
• Protection against device loss (data is still in the cloud).

Important limits

• Sync is not a backup: if you delete a file (or ransomware encrypts it), it is synced everywhere. Additionally use a real backup following the 3-2-1 rule.
• Storage limit: free quota often only 2 to 15 GB.
• Privacy: files lie with a provider, often outside the EU. Encrypt very sensitive things beforehand (for example with Cryptomator).
• Dependence: account blocked or service discontinued? Then data is gone or hard to reach.
• Offline access only for files kept locally.

Using it safely

Enable two-factor authentication, use a strong password, check shared links regularly and do not store passwords or ID copies unencrypted. For company or school data use the services approved by the employer (privacy, data processing agreement).

Alternatives

Syncthing synchronises directly between your devices without a cloud. Nextcloud on your own server or NAS keeps control (self-operation needed). European providers (for example Proton Drive, Tresorit, Ionos HiDrive) advertise special privacy. Check costs, location and features.

See also: Backup strategy, The cloud for beginners, Two-factor authentication, Homelab and self-hosting