How SlipCompare Works
Unlike other document comparison tools that upload your files to remote servers, SlipCompare processes everything 100% locally in your browser. Your documents never leave your device — here's exactly how it works.
Your Files Stay on Your Device
See the difference between how other tools work vs. SlipCompare's privacy-first approach.
Your files are NEVER sent to slipcompare.com or any other server. Zero. None.
❌ Other Tools
- Upload files to their servers
- Files stored (temporarily or permanently)
- Data may be accessed by employees
- Vulnerable to data breaches
- May not be HIPAA/GDPR compliant
✅ SlipCompare
- Files never leave your device
- Nothing stored anywhere
- We literally cannot see your data
- Breach-proof by design
- Safe for any sensitive document
Step-by-Step: How Document Comparison Works
You Open SlipCompare
When you visit slipcompare.com, your browser downloads our web application including all the JavaScript libraries needed to process documents. After this initial load, everything runs locally on your machine.
Browser downloads: mammoth.js (Word), pdf.js (PDF), xlsx.js (Excel), tesseract.js (OCR)
You Upload Documents
Drag and drop or click to select your files. When you "upload," the files are read directly by your browser using the File API — they're loaded into your browser's memory, not sent anywhere else.
FileReader API reads file → Stored in browser memory only
Text Extraction (Local)
JavaScript libraries running in your browser extract text from your documents. For Word files, mammoth.js parses the .docx format. For PDFs, pdf.js extracts text layers. For scanned documents, tesseract.js performs OCR — all locally.
PDF → pdf.js → extracted text
Word → mammoth.js → extracted text
Excel → xlsx.js → extracted text
Image → tesseract.js (OCR) → extracted text
Comparison Algorithm Runs
Our comparison engine uses a Longest Common Subsequence (LCS) algorithm to find differences between the two texts. This runs entirely in JavaScript in your browser, comparing word by word to identify additions, deletions, and changes.
LCS Algorithm: O(n×m) comparison → Diff array generated
Results Displayed
The comparison results are rendered in your browser with color-coded highlighting. Green shows additions, red shows deletions. You can review the side-by-side diff, see statistics, and the AI assistant can help analyze the changes — all while your original files remain on your device.
The Technology Behind SlipCompare
We use industry-standard open-source libraries that run entirely in your browser:
Mammoth.js
Extracts text from Word documents (.docx)
PDF.js
Mozilla's library for parsing PDF files
SheetJS
Processes Excel files (.xlsx, .xls, .csv)
Tesseract.js
OCR for scanned documents and images
LCS Algorithm
Word-level diff comparison engine
Web APIs
FileReader, Drag & Drop, Local Storage
Common Questions
Can you really not see my files?
Correct. We physically cannot see your files because they are never transmitted to our servers. You can verify this yourself by opening your browser's Network tab (F12 → Network) and watching — no file data is ever sent when you compare documents.
What about the AI assistant?
The AI assistant (Adam) is optional. If you use it and share document content in your questions, that specific text is sent to process your request. However, this is opt-in and separate from the core comparison functionality, which remains 100% local.
Does it work offline?
After the initial page load (which downloads the JavaScript libraries), the core comparison functionality works offline. Your browser has everything it needs to process and compare documents without an internet connection.
Is this safe for confidential documents?
Yes. Because processing is local, SlipCompare is suitable for confidential legal documents, medical records (HIPAA-sensitive), financial statements, trade secrets, and any other sensitive materials. The privacy guarantee is architectural, not just policy.
Ready to Compare Documents Privately?
Try it yourself — your files will never leave your device.
Open Document Comparison Tool →