Compare Two PDFs
Identify differences between two versions of a PDF document with visual and textual comparison. Pixel-level visual diff highlights changed regions, while word-level text diff shows added and removed content. Perfect for reviewing document revisions, verifying changes, and ensuring version control accuracy.
What does this tool do?
The Compare tool analyzes two PDF documents to identify differences at both visual and textual levels. The visual diff renders both documents and highlights pixel differences with color overlays. The text diff extracts text content and performs word-level comparison to identify insertions, deletions, and modifications. Switch between views to understand layout changes versus content changes.
How it works
Using MuPDF's rendering and text extraction capabilities, the tool processes both PDFs simultaneously. For visual comparison, it renders each page to images and performs pixel-by-pixel comparison, tinting differing pixels in red and blue for the first and second documents. For text comparison, it extracts text preserving reading order and performs a word-level diff algorithm to identify changes. The side-by-side interface lets you navigate through differences page by page.
Features
- Side-by-side visual comparison with pixel diff overlay
- Word-level text diff for content changes
- Switch between visual and text comparison modes
- Per-page navigation through differences
- Both files processed locally — no uploads to server
- Difference highlighting in red/blue
- Handles documents of different page counts
How to use
- 1
Upload the original PDF
Drag the original or version A document onto the first drop zone. This serves as the baseline for comparison.
- 2
Upload the revised PDF
Drag the revised or version B document onto the second drop zone. The tool prepares both documents for comparison.
- 3
Choose comparison mode
Select Visual Diff for layout and appearance changes, or Text Diff for word-level content changes. Visual mode shows pixel differences; text mode shows word insertions and deletions.
- 4
Review differences
Navigate through pages to compare. Visual mode shows overlays where pages differ. Text mode highlights added words (green) and removed words (red).
Common use cases
Review contract revisions
Compare versions of legal contracts to identify exactly what language changed between negotiation rounds.
Verify document updates
Confirm that requested changes were implemented correctly in updated technical documents, reports, or specifications.
Track document evolution
Compare sequential versions of evolving documents to understand the progression of changes over time.
Quality assurance
Verify that regenerated documents (from automated systems, exports, or conversions) match expected outputs.
Tips & best practices
- Visual diff is sensitive to minor rendering differences — anti-aliasing and font hinting may show as changes even when content is identical
- Text diff is more reliable for content comparison but won't catch layout or image changes
- Documents with different page counts compare up to the shorter document's length
- For minor formatting changes only, use Extract Text on both and compare in a text editor