Your data. Your device. Period.
Compare Spreadsheets Without Uploading
Your files never leave your device. All parsing and diffing runs in your browser. Open the Network tab and verify it yourself.
Compare files privately- 100% client-side
- Zero server processing
- GDPR friendly
- Works offline (free tier)
Why privacy matters for file comparison
Most comparison tools upload your files. Your data ends up on someone else's server. You have no control over how it's stored, who has access, or when it's deleted.
Company security policies restrict uploads. IT won't approve tools that send data to external servers. Getting sign-off takes weeks, and most tools don't pass the review.
Compliance requirements make it risky. GDPR, SOX, HIPAA, financial regulations — uploading sensitive spreadsheets to third-party services creates liability you don't need.
How it works
Open ChangeCheck in your browser — nothing to install, no account needed.
Drop your files — they stay on your device the entire time. Nothing is transmitted.
See every difference — export your results. Check your Network tab to verify.
How it works technically
All parsing and diffing runs in a Web Worker inside your browser. There are no XMLHttpRequests or fetch calls to external servers with your file data. Files exist only in browser memory and are discarded the moment you close the tab.
- Web Worker processes files in your browser
- No network requests with file data
- No cookies or trackers ever touch your file data
- Files discarded when tab closes
- Transparent, deterministic diff logic
Who needs private file comparison
Financial audits
Compare ledgers, trial balances, and financial statements without exposing sensitive numbers to external services.
HR & personnel data
Diff employee lists, salary files, and personal records. No employee data leaves your machine.
Healthcare & legal documents
Compare patient records, contracts, or case data where confidentiality is non-negotiable.
Restricted network environments
Works on air-gapped or locked-down networks. Once the page loads, no internet connection is required.
Privacy & security FAQ
How can I verify my files aren't uploaded?
Open your browser's Developer Tools (F12) and switch to the Network tab before comparing files. You will see zero network requests containing file data. All parsing and diffing runs locally in a Web Worker.
Is this GDPR-friendly?
Yes. Since your files never leave your device, there is no server-side data processing to regulate. No personal data from your spreadsheets is collected, stored, or transmitted.
Can I use this on a restricted or air-gapped network?
Yes, for free comparisons. Once the page is loaded, file comparison runs entirely offline. Paid credits require a brief connection for verification, but your files are still never transmitted.
What data does ChangeCheck collect?
No file data whatsoever. The only data collected is anonymous page view analytics. Your spreadsheet contents, file names, and comparison results never leave your browser.
Do you store my comparison results?
No. Everything runs in your browser's memory. When you close the tab, all data is discarded. There are no accounts, no cloud storage, and no server-side processing.
ChangeCheck vs online comparison tools
| ChangeCheck | Typical online tools | |
|---|---|---|
| File processing location | Your browser | Their server |
| Data retention | None | Varies |
| Works offline | Yes (free tier) | No |
| GDPR compliance | By design | Depends |
| IT approval needed | No | Usually |
Try a private comparison
No signup, no upload, no data collection. Just drop your files and get answers.
Compare files privately