PDF Diff — Compare Two PDF Documents Online
The most powerful free online PDF diff tool to compare two PDF files, find differences between documents, and track changes visually. Whether you need to diff PDF files for legal review, compare contracts, or verify document revisions — this tool handles it all instantly.
100% private and secure — all PDF comparison happens directly in your browser. No uploads to servers, no data collection, no tracking. Works on Mac, Windows, and any platform with a modern browser.
Why Use This PDF Diff Checker?
Unlike other PDF compare tools that require downloads or subscriptions, our online PDF diff checker is completely free, processes files instantly in your browser, and keeps your documents private.
Instant PDF Comparison
Compare PDF files online in seconds. Our optimized diff algorithms extract and compare text with word-level and character-level granularity — no waiting, no processing delays.
100% Private & Secure
Your PDF documents never leave your device. Unlike other PDF diff tools, we don't upload your files to any server. Perfect for comparing confidential contracts and legal documents.
Rich Visual Diff
See differences highlighted directly on the PDF pages with color-coded overlays. Red highlights show removed content, green shows additions — just like track changes in Word.
Multiple Comparison Modes
Choose from six diff views: Rich Text overlay, Plain Text side-by-side, Redline track changes, Image pixel diff, OCR text extraction, and detailed file metadata comparison.
Legal Redline View
Professional redline comparison for legal document review. See insertions underlined in blue and deletions struck through in red — the standard format for contract redlining.
Works Offline
Once loaded, this PDF comparator works without internet. No server dependency means you can compare PDF documents anytime, anywhere — even on flights.
Export Diff as PDF
Export your comparison results as a new PDF document. Rich text diffs include highlighted overlays, image diffs export the visual comparison, and redline exports preserve track changes.
Cross-Platform
Works on Mac, Windows, Linux, and mobile devices. No need to download diff PDF software — just open your browser and start comparing. Replaces desktop tools like DiffPDF.
No Sign-up Required
Start comparing PDFs immediately — no registration, no email, no accounts. This free PDF diff tool respects your time and privacy.
What Can You Compare?
Our PDF diff checker handles any type of PDF document. From legal contracts to technical specifications, financial reports to academic papers — if it's a PDF, you can compare it.
Legal & Contract Review
Compare two PDF contracts to find differences between versions. Our redline view shows exactly what changed — perfect for lawyers, paralegals, and compliance teams reviewing document revisions.
- Contract version comparison
- Legal document redlining
- Policy and terms changes
- Regulatory filing diffs
- NDA and agreement review
Visual Document Diff
Compare PDF files visually with pixel-level image comparison. Highlight mode shows differences in pink, subtract mode reveals only changes, and fade mode overlays both versions.
- Design proof comparison
- Layout and formatting changes
- Brochure and flyer revisions
- Architectural drawing diffs
- Report formatting verification
Text & Data Comparison
Extract and compare text content from two PDFs with word or character granularity. Side-by-side and unified views make it easy to find differences between two PDF documents.
- Financial report comparison
- Academic paper revisions
- Technical specification diffs
- Manual and guide updates
- Data sheet verification
How to Compare Two PDF Files Online?
Comparing two PDFs online is simple. Follow these four steps to diff PDF documents and find all differences between your files:
Upload Original PDF
Drop or select your original PDF document in the left panel. The file is processed entirely in your browser.
Upload Changed PDF
Drop or select the revised PDF in the right panel. Both files are parsed and text is extracted instantly.
View Differences
Switch between Rich Text, Plain Text, Redline, Image, and OCR views to see all differences highlighted.
Export Results
Export the comparison as a PDF with diff highlights, or use the redline export for legal track-changes format.
Pro tip: Use the Rich Text view with "Text" method for the most accurate text-level comparison with position-aware highlighting on the actual PDF pages.
For visual layout changes, switch to the Image tab and use "Highlight" mode to see pixel-level differences between the two PDF documents.
Frequently Asked Questions
What is a PDF diff tool?
A PDF diff tool (also called PDF compare tool or PDF difference checker) compares two PDF documents and highlights the differences between them. It shows text additions, deletions, and modifications, making it easy to see exactly what changed between two versions of a document.
How do I compare two PDF files online?
Simply upload or drag-and-drop your original PDF in the left panel and the changed PDF in the right panel. Our PDF diff checker instantly extracts text and highlights all differences — red for removed content, green for additions. No software download required.
Is this online PDF diff checker free?
Yes, this PDF diff tool is 100% free for both personal and commercial use. No sign-ups, no usage limits, no hidden fees, and no premium tiers. Compare as many PDF files as you need.
Is my data secure when comparing PDFs online?
Absolutely. All PDF comparison happens locally in your browser — your documents are never uploaded to any server. This makes it safe for comparing confidential contracts, legal documents, and sensitive business files.
Can I use this as a diff PDF tool on Mac?
Yes! This PDF diff tool works on Mac, Windows, Linux, and any platform with a modern browser. It replaces desktop applications like DiffPDF for Mac without requiring any installation.
How does the redline comparison work?
The redline view shows a legal track-changes style comparison. Removed text appears in red with strikethrough, and added text appears in blue with underline — the standard format used in legal document review and contract redlining.
Can I find differences between two PDFs visually?
Yes! The Image tab provides pixel-level visual comparison with five modes: Highlight (shows differences in pink), Split (side-by-side), Fade (overlay with opacity), Slide (swipe comparison), and Subtract (shows only pixel differences).
Can I export the PDF diff results?
Yes, you can export comparison results as a new PDF. Rich text diffs include highlighted overlays on the actual pages, image diffs export the visual comparison, and redline exports preserve the track-changes format with colored text and strikethrough.
Does this tool work offline?
Yes, once the page loads, you can compare PDF documents without an internet connection. All processing — text extraction, diff computation, and rendering — happens entirely in your browser.
What's the difference between the comparison modes?
Rich Text shows diffs overlaid on actual PDF pages. Plain Text extracts and compares raw text side-by-side. Redline shows legal track-changes. Image compares pages as pictures pixel-by-pixel. OCR extracts text from rendered pages. Details shows file metadata.