You copied your work folder to an external drive, or your backup app says it finished. Before you wipe the laptop, hand over the drive, or delete the originals, you want to know two things: is everything in the backup, and is every copy still good?
To verify a backup folder, compare it with the original and check the contents of the files, including those whose names, sizes, and dates still match. Diff Anything does this locally on Mac or Windows and lists missing, changed, and unverified files. Your files stay on your computer, with no AI involved.
Why a finished backup is not proof
A copy can finish without errors and still leave you with less than you think. Files created after the backup ran are not in it. A file that was open or locked during the copy can be skipped. A drive can return a damaged copy that still has the right name, size, and date.
Comparing file names and sizes in two windows does not catch the last case, and opening every file by hand takes time. A folder comparison checks the included files and subfolders together and shows what needs your attention.
How to compare a backup with the original folder
- Connect the backup drive, or open the backup location, so you can see the backup as a normal folder.
- Open Diff Anything and click Compare two folders.
- Choose the original folder first, then the backup. You can also drop both folders onto the window.
- For an exact copy check, use the hash and folder settings below.
- Read the summary. Subfolders are included, and files that match are hidden, so the list shows only the differences.
Compare matching levels: the original project folder with the same folder in the backup, not with the drive or parent folder that contains it. Otherwise every file shows up as missing.
If your backup app stores versions in its own format, restore the version you want to check to a separate folder first. Compare that restored folder with the corresponding original. Pause edits while you compare so the files stay consistent.
What the result tells you
With the original on the left and the backup on the right, each difference has one of these labels:
| Label | What it means | What to do |
|---|---|---|
| Left only | The file is in the original but missing from the backup. | Copy it to the backup, or find out why the backup skipped it. |
| Changed | The file is in both folders, but the content is different. | Check whether the original was edited after the backup ran, or whether the backup copy is damaged. |
| Right only | The file is only in the backup. | Usually a file you deleted or renamed after the backup. Keep it if you still need it. |
| Moved | The same file is in both folders, at a different path. | Nothing is lost. The file was moved to another folder. |
| Unverified | The content was not checked, for example because the file is large or could not be read. | Check the row’s explanation, enable Compare hashes if needed, and compare again. |
Each side shows the file’s size and modified date. With content checks enabled, Diff Anything compares what is inside the files, not only their names and dates. A Changed result tells you the copies differ; it does not tell you which copy is correct or whether either is damaged. Review the file before replacing it.
To see what does match, choose Identical. Choose All to go back to the differences.
Backup verification settings for an exact copy
Open Folder options and choose what you want to verify. For matching file contents, use these settings:
- Compare hashes. By default, a file over 5 MB with the same size on both sides can be marked Unverified when its content was not read. Turn on Compare hashes to check file contents, including large videos, photos, and archives.
- Compare JSON, YAML, and other data files by their data. Turn this off for an exact copy check. When it is on, data files can count as identical even when their formatting or key order differs.
- Compare archives by their contents. Turn this off to check the archive files themselves. When it is on, archives with the same entries can match even if their compression or internal timestamps differ.
- Hidden files. Files and folders whose names start with a dot are left out until you turn Hidden files on. Turn it on if those belong in the backup.
- Ignore patterns. Developer folders such as .git, node_modules, build, dist, and vendor are ignored by default. Remove any pattern that excludes something you need in the backup, and review any include patterns or .gitignore filtering you have enabled.
A result with no differences means the included files match under those settings. Review excluded files, Unverified entries, and moved files before calling the backup an exact copy. Permissions and timestamps have separate options, and symbolic links are compared by their targets rather than followed by default.
After the check
Bring the backup up to date with your usual backup app or by copying the missing and changed files. Then click the reload button on the backup’s side. When everything matches, Diff Anything shows No differences found.
With Pro, you can do more from the same result:
- Copy the missing and changed files to the backup from the comparison, with a preview of every change and undo.
- Export the comparison as an HTML report to keep a record of what you checked.
- Save a snapshot of a folder and later compare the folder with it, to see what changed since the backup.
The same check works for other copies you need to trust: a client delivery before you send it, a photo archive moved to a new drive, or a project folder copied to a new computer.
For a backup you may need to restore, also open a few important files from the restored copy in their usual apps. A matching folder confirms the comparison; a restore check confirms you can use those files when you need them.
Try it with your next backup
Pick one folder you care about and its backup. Apply the exact copy settings above, then review what is missing, changed, moved, or unverified before you depend on that copy.
Check what made it into your backup
Compare locally on Mac or Windows. No upload, no account, and no AI involved.
Free includes up to 10 comparisons per day; a folder comparison lists its first 100 results. Use Pro to review more than 100 results. Pro is a one-time purchase that removes the preview limit and adds folder copy and sync, reports, and snapshots.For every folder option, see how to compare two folders on a Mac, how to compare two folders on Windows, or the folder compare tool.