How do I check that a backup actually works?
Quick answer
Restore a small, representative set of files to a new, separate folder—not over your originals. Compare the restored files with what you expected, check names and sizes, and open a few files using their usual apps. For a full-device or app backup, follow its restore-test option or instructions and avoid testing on your only working copy. CISA advises testing backup procedures, but its guidance is for water-system environments, not consumer-specific restore steps. [S1]
The question, the details, the next step.
How do I check that a backup actually works without risking the files I have now?
Treat the test as a copy-out exercise, not a recovery of your everyday device. Choose a separate destination, such as a new folder named [Backup test – date]. Restore a small set of files there first, and do not select an option that replaces or synchronizes your existing files.
For example, if your backup contains photos, documents, and a project folder, choose one or two items from each group. A test with only one tiny text file may show that one file can be restored, but it does not check whether other folders or file types are included. CISA recommends testing backup procedures; its cited fact sheet concerns water systems and does not specify a consumer test location or step-by-step method. [S1]
What should I choose for the test? I don't want to restore everything.
Make a short sample that represents what you would actually need after a problem. Include different folders or file types, and at least one item you know should be in the backup. If you have a particularly important file, include it, but keep the test restore separate from the original.
Before restoring, write down what you expect to find: for example, [three documents], [two photos], and [one project folder]. The counts are placeholders; use your own. If the backup tool lets you browse its contents, compare that view with your list. That is a useful preliminary check, but it is not the same as restoring and opening the files.
Once the files are restored, how do I tell if they're complete?
Check in layers:
- Compare the restored names and folder structure with your expectation list.
- Check whether the expected number of items is present. Look for folders that are unexpectedly empty or missing.
- Compare file sizes with the originals when you can. A size difference can be a reason to investigate, but by itself it does not prove a file is damaged.
- Open a few restored files in the usual apps. For photos, view them; for documents, check that the expected pages or content appear; for audio or video, play a short portion.
If a file will not open, appears incomplete, or is missing, stop and keep both the original and the backup unchanged while you investigate. Do not treat a successful test of a few samples as proof that every backed-up item is good.
My backup is for an app or a whole device, not just a folder. Is the same test okay?
Not necessarily. Restoring a full-device or app backup may replace settings or data, so first check the backup tool's instructions for a test, preview, or non-destructive restore option. Do not experiment on your only working device or account. If the tool has no safe test option, ask its support team or a qualified technician how to verify it without overwriting current data.
For a folder-based backup, the separate-folder sample test is a straightforward way to check selected files. For a full-system backup, a handful of extracted files may confirm those files are accessible, but it does not establish that the whole device can be recovered. CISA's advice supports testing backup procedures, but does not establish consumer-specific steps or guarantee any particular backup's completeness. [S1]
Can you give me a simple record I can keep so I know what I tested?
Copy and fill in this record after each test:
Backup tested: [name or description] Date: [date] Restore destination: [separate folder or other safe location] Items expected: [names, folders, or counts] Items restored: [names, folders, or counts] Checks completed: [names/structure] [sizes] [opened in usual apps] Result: [all sampled items usable / issue found] Next action: [none / investigate missing or unusable item]
Worked example, using placeholders: Backup tested: [Home files backup]. Expected: [2 documents and 1 photo]. Restored to: [Backup test – date]. Checks: [all three names present; opened both documents and viewed the photo]. Result: [sample passed]. This records only what was tested; it does not claim that every item in the backup is complete.
A practical checklist
Choose a small but representative set of expected files or folders.
Select a new, separate restore destination; do not overwrite or sync over originals.
Compare restored names, folder structure, and expected item counts.
Check file sizes when useful, then open representative files in their usual apps.
Record what you tested and keep originals unchanged if anything is missing or unusable.
For full-device or app backups, use documented safe test steps or ask for qualified help.
A few more useful answers
Does seeing files listed in a backup prove the backup works?
No. A listing shows what the tool displays, but a separate restore and opening representative files checks more of the process. Even a successful sample does not prove every item is recoverable.
How often should I test a backup?
Choose a repeat interval that fits how often your important files change, and test again after changing your backup setup. The supplied source recommends regular testing but does not set a consumer schedule. [S1]
What if one restored file is missing or will not open?
Keep the original and backup unchanged, note exactly what failed, and check the backup tool's instructions or get qualified support before attempting a broader restore.
Sources
References used for this guide.
- [S1] Top Cyber Actions for Securing Water Systems cisa.gov · Checked