What would I actually lose if my computer died tomorrow?

There is a useful distinction that makes this exercise quick. Anything you could re-download or re-install costs you time. Anything that exists only on your machine costs you the thing itself. Almost all backup effort should go to the second group, and most people's backup is quietly aimed at the first.

Step by step

1. Category one: irreplaceable originals.Photographs and video you took, scans of documents and old prints, writing, recordings, drawings, project files. Nothing on earth reproduces these. They are the reason backups exist and they are usually the easiest to find, because they sit in obvious folders.
2. Category two: records you would have to reconstruct.Statements, tax working, invoices, warranty and receipt scans, correspondence about a purchase or a dispute, meter readings, house paperwork. Individually replaceable with effort; collectively, weeks of your life.
3. Category three: data that lives inside a program.This is the group people miss. Locally stored email, notes apps that do not sync, a password manager's local vault, browser bookmarks and saved logins, accounting software files, photo-editing catalogues holding all your edits, and game saves. Some sit in hidden application-data folders that a simple documents backup will not touch.
4. Category four: keys to everything else.Two-factor recovery codes, an authenticator app that only exists on this machine, encryption keys, licence keys, and the details of the email account used to reset everything else. Losing these can lock you out of accounts that hold the rest of your life.
5. Category five: configuration.Not critical, genuinely annoying: bookmarks, custom templates, keyboard shortcuts, software settings, the printer that took an afternoon to get working. Worth a note of what matters rather than a backup.
6. Write the list on paper, in one page.One line per item, with where it lives. This document is worth more than most backup software, because it converts "back up my computer" into a checkable list.
7. Check each line against your backup, individually.Open the backup and confirm the file or folder is present, not merely that the backup ran. Application-data folders and email stores are where this check most often fails.
8. Fix the gaps and re-run.Usually two or three lines need adding: an email export, a password vault export kept encrypted, and a photo-editing catalogue. Add them, run the backup, check again.

Tips

• Sort your user folder by size once. Large files are usually replaceable media; the irreplaceable material is often small and easy to overlook.
• Search your drive for your own name and for the current and previous tax years. It surfaces documents filed in odd places.
• If a program stores everything in one database file, back up that file specifically rather than trusting a folder-based backup to find it.
• Do this once a year. New categories appear — a new app, a new obligation, a new camera — and the list is much quicker to update than to write.

Checklist

• Photographs and video, including anything still only on a camera card
• Scans of documents, certificates and old family prints
• Writing, projects, and anything creative in progress
• Financial records and tax working for the years you must retain
• Warranty, receipt and insurance paperwork
• Locally stored email and its folders
• Notes and to-do apps that do not sync
• Password manager vault and two-factor recovery codes
• Browser bookmarks and saved data
• Photo-editing catalogue or library file, not just the images
• Accounting or business software data files
• Licence keys and software you paid for
• Game saves that are not stored in the cloud
• Anything on the desktop, which is where unfiled work hides
• The list itself, kept somewhere other than this computer

Questions people ask