What a backup actually is
A backup is a separate copy of a file that you can use if the original is lost, damaged or changed by mistake. The word “separate” carries most of the weight. A second folder on the same drive is convenient for experiments, but if the drive fails, both copies go with it. Likewise, a file that syncs between your laptop and your phone may not be a backup at all, because deleting it in one place can delete it everywhere.
The general idea is simple: keep more than one copy of what matters, and keep those copies in different places. Almost everything else is about how much effort that should take for you.
The common ways files get lost
It helps to think about what you are protecting against, because different risks call for different copies.
- Hardware failure. Drives, phones and laptops wear out, and sometimes without warning.
- Loss or theft. A bag left on a train takes its contents with it.
- Accidental deletion or overwriting. This is probably the most common problem, and it happens to careful people too.
- Malicious software. Some programs lock or damage files, and they can reach any drive connected at the time.
- Account problems. A cloud account can be locked or closed, and a service can change its terms or shut down.
- Fire, flood or other damage at home. Copies stored in the same room may all be affected at once.
No single copy protects against all of these, which is why having a few in different places is the usual advice.
A simple rule of thumb: three copies, two types, one elsewhere
A widely repeated guideline is sometimes called the 3-2-1 idea. It means having three copies of important data in total (the original plus two backups), stored on two different kinds of storage, with one copy kept in a different location from the rest.
For a typical household, this might look like:
- The original files on your computer.
- A second copy on an external drive kept at home.
- A third copy in an online storage service, or on a drive stored at a relative’s home or another site.
This is a guideline, not a law. A student with a few essays and a family with ten years of photos have different needs. Treat the idea as a way to check whether any single event could wipe out everything you care about.
Decide what is worth backing up
You do not need to copy everything. Start with items that would be hard or impossible to replace:
- Photos and videos, especially family ones
- Tax records, contracts, insurance papers and other household paperwork in scanned form
- Work projects, writing and creative files
- Notes and personal records
- Exported lists of account information and settings that would take a long time to rebuild
Programs and the operating system can usually be reinstalled, so they are lower priority. If your files are already arranged in a clear structure, as described in the guide to file organization, deciding what to copy gets easier because you can back up a few top-level folders instead of hunting for individual files.
Make it automatic where you can
A backup that depends on remembering tends to lapse. Many computers and phones include a built-in backup option, and many external drives and online services offer scheduled copies. Setting one up once, so that it runs on its own, is usually more reliable than a monthly manual copy.
If you prefer manual backups, tie them to something regular. Some people copy their important folders at the end of each month, or when they pay bills. If you rely on a prompt, recurring task reminders work better than a one-time note.
How often is often enough? A useful question is how much work you could stand to redo. If you could easily recreate a week’s changes, weekly backups may be fine. If you work on something valuable every day, you will probably want something more frequent or continuous.
Test your backups
A backup you have never opened is a guess. Problems are surprisingly common: a scheduled job that stopped running months ago, a drive that is full, a folder that was never included, or a file format that can no longer be opened.
Every few months, try restoring a handful of files from each backup to a different location and open them. Check dates too, to confirm the backup is recent. This takes ten minutes and tells you far more than a status message saying the job completed.
Think about privacy and security
Copies of your files are also copies of whatever sensitive information they contain. A few general points apply:
- Encrypting external drives and online copies can reduce the harm if a drive is lost. Many systems offer this as a built-in setting.
- Protect any online storage account with a strong, unique password and, where offered, an additional sign-in step. Sensible password habits matter here because one compromised account could expose every file you have stored.
- Keep a record of where your backups are and how to access them, somewhere other than the computer being backed up. If the person who set things up is not available, someone else in the household should still be able to find the files in an emergency.
A modest setup you actually maintain is better than an ideal one you never finish. Pick one place for a second copy, one place away from home for a third, check them every so often, and adjust as your files grow.