Compare PDFs (Free, Private, No Upload)

PDF comparison enables version control, contract review, and change tracking by identifying visual differences between documents. This tool compares two PDF files directly within your browser, making it perfect for reviewing contract revisions, comparing design mockups across iterations, verifying document changes before signing, or tracking modifications in legal agreements. Because everything happens locally on your device, sensitive information in confidential contracts, proprietary designs, financial statements, or privileged documents never leaves your computer. This privacy-preserving architecture is essential when working with attorney-client privileged materials, trade secrets, merger agreements, or regulated data that cannot be uploaded to third-party services. The comparison tool offers three viewing modes: side-by-side display shows both documents simultaneously for manual comparison, overlay mode superimposes one document over the other with adjustable transparency to spot layout shifts and text changes, and difference highlighting mode automatically detects and marks changed areas in red (major differences) or yellow (minor variations). Unlike simple checksum comparisons that only detect whether files differ, visual comparison shows exactly what changed and where. This is invaluable for reviewing contract redlines where a party might have modified terms subtly, or for QA testing where design specifications must match implementation precisely. The page-by-page comparison handles multi-page documents systematically, ensuring no changes are overlooked in lengthy agreements or reports. Adjustable opacity in overlay mode helps identify subtle formatting changes, text reflows, or image repositioning that might otherwise escape notice. The difference detection algorithm performs pixel-level comparison, catching even minor variations in fonts, spacing, or image quality. This comprehensive comparison capability rivals expensive desktop PDF tools while maintaining complete privacy and requiring no software installation. Legal professionals use it for contract redline verification, designers use it for mockup iteration tracking, compliance teams use it for policy document change validation, and academics use it for dissertation revision tracking.

  1. Upload the first PDF (original version) by clicking Select First PDF or dragging it onto the drop zone.
  2. Upload the second PDF (modified version) by clicking Select Second PDF or dragging it.
  3. Choose a view mode: side-by-side, overlay, or highlight differences.
  4. In overlay mode, adjust the opacity slider to better see differences.
  5. Use the arrow buttons to navigate through pages systematically.
  6. Examine highlighted differences (red for major changes, yellow for minor variations).

Related tools: Merge PDF, Split PDF, Annotate PDF

FAQ

What types of differences can this detect?

The comparison tool detects visual differences including text changes, formatting modifications, image alterations, layout shifts, page size differences, and element repositioning. It performs pixel-level comparison, so even subtle changes like font variations or spacing adjustments are detected.

Can it compare text content accurately?

This tool performs visual comparison (pixel-by-pixel), not semantic text comparison. It will detect text changes visually but won't produce a word-by-word text diff. For detailed text change tracking with edit history, consider specialized document comparison software that performs semantic text analysis.

What if the PDFs have different page counts?

The tool will compare corresponding pages (page 1 with page 1, etc.) up to the shorter document's length. Pages beyond that in the longer document won't have comparisons. The tool displays a warning when page counts differ so you're aware of structural differences.

How accurate is the difference detection?

Difference detection uses pixel-level comparison with adjustable sensitivity thresholds. Major differences (text additions/deletions, image changes) are highlighted in red with high confidence. Minor differences (subtle formatting, anti-aliasing variations) appear in yellow. Very subtle rendering differences may not be detected.

Can I export the comparison results?

Currently, the tool provides interactive comparison viewing but doesn't export merged diff PDFs or comparison reports. You can take screenshots of the comparison view for documentation purposes. For exportable comparison reports, consider enterprise PDF comparison tools.