Find visual differences, deleted paragraphs, added clauses, and layout shifts between two PDF documents.
Synchronized split view, pixel-by-pixel diff overlay, and downloadable audit reports.
No Server Uploads Side-by-Side Synced Scrolling Pixel Diff & Bounding Clouds Free & Unlimited
Document A (Original)
Original PDF
Drag & drop baseline file, or
Swap
Document B (Modified)
Modified PDF
Drag & drop revised file, or
Don't have files ready?
Page 1 of 1
Fit Width
Sensitivity:35
Removed in Doc B (Red)
Added in Doc B (Green)
Modified (Amber)
Unchanged Text
Document A (Original)Baseline
Document B (Modified)Revision
Changes Inspector1 Page
Comparing documents...
Step-by-Step Guide
How to Compare Two PDF Files Online
Effortlessly detect revisions, redlines, and layout changes between contracts, invoices, and legal drafts in seconds.
01
Upload Original PDF
Drag & drop or browse the baseline version of your document into Slot A. Files are processed entirely in browser memory.
02
Upload Revised PDF
Upload the revised or modified PDF into Slot B. If either file is password protected, enter the decryption passphrase.
03
Choose View Mode
Switch between Side-by-Side split view and Pixel Diff overlay (with Highlight Clouds, Delta Mask, and Flicker A/B).
04
Inspect & Export Report
Inspect differences with real-time badges or jump across pages with the Change Inspector, then export a PDF Comparison Audit Report.
Comparison Modes
Engineered Inspection Capabilities
Different document workflows require different comparison techniques. PDFMaster gives you precision diff modes and tools in one unified studio.
1. Side-by-Side Split View
Displays Document A and Document B side-by-side with synchronized scrolling and zoom. When you pan or zoom in one pane, the other tracks in lockstep, making manual review natural and effortless.
2. Visual Diff (Pixel Overlay)
Superimposes both pages and renders pixel deltas with smart color coding: deleted content is highlighted in vibrant Red, additions in Green, and identical context in low-contrast grayscale.
3. Rapid Flicker A/B Mode
Alternates rapidly between Document A and Document B right in your viewport. Because the human eye detects motion instantly, subtle margin slips, font shifts, or nudge edits immediately pop out.
4. Change Inspector & Audit PDF
Browse page-by-page revision statuses in the interactive side drawer, jump straight to modified sheets, and download a comprehensive Executive Comparison Audit Report with one click.
Enterprise Capabilities
Engineered for Precision, Speed & Privacy
Designed from the ground up for attorneys, engineers, auditors, financial analysts, and researchers.
100% Client-Side Privacy
Your sensitive contracts, proprietary blueprints, and personal statements never touch any remote server. All parsing, rendering, and diff calculations happen inside your local browser sandbox.
One-Click Difference Navigator
Never manually hunt through hundreds of pages. Use the Prev Change and Next Change buttons to automatically scroll and zoom directly to the exact page and paragraph containing modifications.
Downloadable PDF Audit Report
Generate a formal Comparison Summary Report in PDF format. Includes executive similarity score, timestamps, file sizes, and a detailed page-by-page table suitable for legal audit trails.
IndexedDB Session Recovery
Accidentally closed your tab or refreshed your window? PDFMaster retains your comparison workspace locally in IndexedDB, allowing you to restore your documents with a single click.
Instant Document Swapping
Accidentally uploaded the revised draft in Slot A and the original in Slot B? Hit the Swap button to instantly reverse roles without having to re-upload your files.
Adjustable Diff Sensitivity
Tweak the delta sensitivity threshold slider to ignore minor anti-aliasing fuzziness or font rendering differences, ensuring you only catch genuine substantive modifications.
Direct Benchmark
PDFMaster vs Paid Desktop Software & Cloud Uploaders
See how our client-side architecture compares against legacy cloud services and expensive subscriptions.
Feature / Metric
PDFMaster (Client-Side)
Cloud Uploaders (Diffchecker/Draftable)
Adobe Acrobat Pro DC
Data Privacy & NDA Safety
100% On-Device (0 Server Uploads)
Uploaded to third-party cloud servers
Local Desktop App
Price / Cost
100% Free Forever
$15 - $30 / month
$239.88 / year
Comparison Modes
Side-by-Side & Pixel Diff with Submodes
Side-by-Side or Text only
Visual Diff & Summary Report
Visual Diff Submodes (Highlights, Mask, Flicker)
Included & Interactive (3 Submodes)
Not Available
Limited / Complex
Audit Report Export (PDF)
Instant Download (jsPDF)
Paywalled / Premium Only
Included
Offline Support
Full Offline Support (Service Worker)
Requires Active Internet Connection
Offline Desktop
Account Sign-up / Login
None Required (Instant Access)
Required for large files
Adobe Creative Cloud Login Required
Frequently Asked Questions
Everything You Need to Know About PDF Compare
Got questions? Here are detailed answers on how PDFMaster compares documents safely and accurately.
How does PDFMaster compare two PDF files?
PDFMaster uses client-side WebAssembly and canvas rendering engines. It parses text content using PDF.js to perform an LCS (Longest Common Subsequence) word-level comparison while simultaneously rendering high-DPI raster layers to compute a pixel-by-pixel visual difference overlay. Any text or layout differences are highlighted with Red (deletions) and Green (additions).
Are my confidential contracts or NDA documents safe?
Yes, absolutely 100%. PDFMaster runs entirely in your local browser sandbox. Your PDF files, extracted text, and rendered comparison pages never leave your device and are never transmitted over the internet to any server. You can even disconnect your internet connection or use Airplane Mode and the tool will continue working flawlessly.
What happens if the two PDFs have different numbers of pages?
PDFMaster handles documents of unequal lengths seamlessly. The total comparison count adapts to the maximum number of pages between both documents. Pages that exist in Document B but not Document A are flagged as added pages in the Changes Inspector drawer.
Can I export a PDF comparison report to share with colleagues or clients?
Yes! Simply click the "Export Audit Report (PDF)" button in the lower toolbar. PDFMaster will compile a professional Executive Comparison Audit Report containing timestamps, file metadata, similarity percentages, and a page-by-page change breakdown table.
What is the difference between Side-by-Side view and Visual Diff?
Side-by-Side view presents Document A (Baseline) and Document B (Modified) alongside each other with synchronized scrolling and zoom controls, allowing you to read both versions in parallel. Visual Diff superimposes both documents on top of each other and highlights pixel changes: additions appear in green, deletions in red, and identical sections are rendered in low contrast. You can also switch between Highlight Clouds, Delta Mask, and Rapid Flicker submodes.
Does PDFMaster support password-protected PDF files?
Yes. If either Document A or Document B has password encryption, PDFMaster will prompt you for the decryption passphrase and unlock it locally in memory using WebAssembly. Alternatively, you can use our dedicated Unlock PDF tool to permanently remove passwords.
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