Backup Compare — Compare Backup Files Online Free
Is last night's backup actually right? Compare two backup files and see what changed between snapshots — verification, not hope. Free, no registration, contents never stored.
How to Compare Backup Files Online
Here is the fastest way to diff two .bak files with Backup Compare:
- Load the original .bak file on the left side.
- Then paste the updated .bak file in the right editor.
- Run Compare and review additions in green, deletions in red.
Tip: compare a fresh backup against the previous one right after each migration — verifying now beats discovering at restore time. Available in any recent browser — Chrome, Firefox, Edge, or Safari — on all major desktop and mobile platforms, with no limit on comparisons. Side-by-side comparison costs nothing and requires no account; Premium unlocks the line-by-line analytical view.
Understanding the Backup File Format
.bak is the conventional extension for backup copies — most prominently SQL Server database backups, but also editor and application backup files created before risky changes. A backup is only valuable if it's intact and you know how it relates to the current file, so backup file integrity checks and version comparison matter: confirming a backup hasn't been corrupted or tampered with, and seeing what changed since it was taken. Understanding what's inside a .bak file is half the job; the other half is verification, and backup file comparison is the only honest answer to whether a restore point is truly good.
Common Uses of Backup Files
The everyday scenarios it was built for:
- DBAs verify a nightly SQL dump differs from yesterday's in exactly the expected tables.
- Sysadmins compare config backups before and after a maintenance window.
- IT auditors document backup-to-backup changes for compliance evidence.
- Engineers check a pre-migration backup against the post-migration export.
- Ops teams confirm a restore candidate matches the state they intend to recover.
- Administrators detect a backup job that silently stopped capturing new data.
Auditors love a clean before-and-after diff far more than a promise that the backup should be fine.
Differences Detected in Backup Files
The tool performs backup version diff at the content level: for text-based backups it highlights every changed, added, and removed line; for verification workflows it confirms whether two files are byte-identical — an instant backup file hash check equivalent. Backup data integrity issues like truncation, corruption-induced differences, or unexpected post-archive edits surface immediately.
Examples of Changes Found in Backup Files
What a snapshot-to-snapshot comparison typically reveals:
- A config.bak compared against the live config showing exactly which settings changed since the backup was taken — the rollback delta in one view.
- Two nightly backup generations where the newer file is unexpectedly identical to the older one, revealing a stalled backup job.
- A .bak that should match its archive copy but differs in three lines — evidence of post-archive modification.
- A restored file verified byte-for-byte identical to its backup before being promoted to production.
- Seven consecutive nightly dumps that were byte-identical — the comparison revealed the backup job had been exporting a stale snapshot for a week.
Why Use FileDiffs for Backup Comparison
A backup you can't verify is just a file you hope is correct. FileDiffs answers the question every restore plan depends on, comparing two snapshots in the browser to show exactly what changed and, just as usefully, what suspiciously didn't. It's scoped honestly to text-based backups like SQL dumps and config exports, and the page is built around the real verification moments DBAs and sysadmins face, with examples like seven identical nightly dumps that reveal a backup job silently stuck on stale data.
Frequently Asked Questions About Compare BAK Files Online
Upload the backup and its counterpart (the live file, or another backup generation) and the tool reports every difference — or confirms the files are identical. This works best with text-based backups such as SQL dumps and config exports, where every line is comparable.
Compare the backup against a known-good copy or its source. An identical result confirms integrity; any unexpected difference flags possible corruption or tampering. A backup that differs from its source in unexpected places is a restore-day disaster caught early.
Upload both generations and review the highlighted changes — this shows exactly what changed between backup points, useful for audits and recovery planning. Compare consecutive snapshots after each scheduled job — identical files may signal a backup process that silently stopped updating.
Full binary .bak database backups are best compared by restoring and diffing schema/data with database tools; for script-based and text backups, this tool gives a direct line-level comparison. For script-based dumps, the comparison shows schema and data changes side by side between backup generations.
Compare the current file against the archived backup. Identical means untouched; any reported difference shows precisely what was modified and where. Unchanged backups across days deserve suspicion too: verify the job is actually capturing new data.
Yes. Backup contents are compared locally in your browser and never uploaded to a server, so database dumps and config backups stay confidential. Nothing is stored, and the data is cleared when you close the tab.