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PDF Compare (Visual Diff)

Compare two PDF files side by side — highlights pixel-level differences between documents.

100% Client-Side — files never leave your device

What is PDF Compare (Visual Diff)?

PDF Compare is a free online tool that lets you compare two PDF files and see exactly what changed between them. Upload two PDFs and the tool renders each page at the same resolution, then performs a pixel-level comparison. Differences are highlighted in red on a grayscale background. View results side-by-side or in diff view, navigate through all pages, and see the difference percentage for each page. Perfect for comparing document revisions, contract changes, or design iterations.

How to Use PDF Compare (Visual Diff)

  1. 1

    Upload PDF A

    Drop or click to upload the original PDF document in the left panel.

  2. 2

    Upload PDF B

    Drop or click to upload the modified PDF document in the right panel.

  3. 3

    Compare

    Click Compare. Each page is rendered and compared pixel by pixel.

  4. 4

    Review differences

    Navigate pages with arrows. Red areas show differences. The percentage indicates how much of the page changed.

  5. 5

    Switch views

    Toggle between Side by Side (see both versions) and Diff View (red overlay on grayscale) for different perspectives.

Features

  • Pixel-level visual comparison
  • Red overlay highlights all differences
  • Side-by-side and diff overlay views
  • Per-page difference percentage
  • Color-coded page indicators (green/yellow/red)
  • Handles different page counts gracefully
  • Navigate through all pages
  • Configurable sensitivity threshold
  • 100% client-side — files never uploaded
  • No signup, no watermarks, no limits

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Frequently Asked Questions

How does the comparison work?+
Both PDFs are rendered to the same resolution. Each pixel is compared and if the color difference exceeds a threshold, it is highlighted in red on the diff view. Matching pixels are shown in grayscale.
What counts as a difference?+
Any pixel where the combined RGB color distance exceeds 30 (out of 765 max). This means very subtle anti-aliasing differences are ignored, but any meaningful visual change is caught.
Can I compare PDFs with different page counts?+
Yes. The tool compares up to the maximum page count. Extra pages from the longer document are compared against blank white pages.
Are my files safe?+
Yes. Both PDFs are processed entirely in your browser. Nothing is uploaded to any server.
Why is there a small percentage even for identical files?+
PDF rendering can have minor anti-aliasing differences between runs. Values below 0.5% typically indicate identical content.
Can I compare specific pages only?+
The tool compares all pages automatically. Use the page navigation to jump to the page you are interested in.
Does it detect text changes specifically?+
The comparison is visual (pixel-based), not text-based. Any visual change — text, images, layout, colors — is detected. For text-only diffs, use our Text Diff Checker.
What about scanned documents?+
Scanned PDFs compare just fine since the tool works with rendered pixels. However, slight scanning variations (tilt, exposure) may show as differences.