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PDF Compare

Compare two PDFs locally to find added or removed pages plus visual and text changes.

View on GitHub
Local processing
About your filesFiles and content selected in this tool are processed in your browser and are not uploaded to a Browser Kitty backend.
Operation demo See the basic workflow in a short video.

About this tool

PDF Compare loads a before and after PDF and helps identify page-structure, visual, and text changes. Instead of simply comparing page 1 to page 1, it uses page appearance and extracted text to estimate which pages correspond to each other.

This helps avoid marking every later page as changed when a page is inserted or removed in the middle. Selected pages can be aligned before comparison and reviewed using difference, side-by-side, overlay, slider, or blink views.

Good for

  • Review what changed between revisions of estimates, drawings, forms, or reports
  • Compare long PDFs even when pages were inserted or removed in the middle
  • Check both visual differences and text changes when the PDF contains extractable text

What it can do

Key capabilities available in this tool.

How to use

  1. Select the original PDF as Before and the revised PDF as After.
  2. After analysis, review the summary of matched, changed, added, and removed pages.
  3. Choose a page pair from the list. You can filter the list to changed pages only.
  4. Switch among difference, side-by-side, overlay, slider, and blink views, and adjust sensitivity or render quality when needed.
  5. Optionally export the current visual difference as PNG or the document-wide comparison result as CSV.

Supported

  • Input: a Before and After PDF, including password-protected PDFs.
  • Matching: automatically aligns the page sequence using page appearance, extracted text, and page aspect ratio.
  • Views: difference, side-by-side, overlay, slider, and blink, with 50–400% zoom.
  • Output: difference PNG for the current page and a CSV report for the document-wide comparison.

Limitations and notes

  • PDFs that contain only scanned text images do not provide text differences; comparison relies mainly on visual differences. This is not an OCR tool.
  • Scanning noise and anti-aliasing can produce small differences that are not real content changes. Adjust sensitivity and small-difference filtering as needed.
  • Very large PDFs or high-detail rendering can use significant device memory and take longer to analyze.
  • Difference results are an aid to review and do not guarantee final verification of contracts, drawings, or other critical documents.

Frequently asked questions

Are the PDFs uploaded to a server?

No. PDF loading, page analysis, rendering, matching, and difference calculations are performed in the browser.

Can it compare PDFs when pages were inserted in the middle?

Yes. Page sequences are matched using visual and text similarity rather than page numbers alone, allowing inserted and removed pages to be detected.

Can it detect text changes in scanned PDFs?

If a scanned page has no embedded text, text differences are unavailable, but changes can still be reviewed through visual comparison.

Can I save the comparison results?

Yes. Export the current page difference as PNG and the document-wide comparison summary as CSV.

Offline version and source code

The root-level pdf-compare.html on GitHub is a standalone HTML file with the required PDF.js assets bundled inside. Download it to run PDF comparison locally on your device.

View source on GitHub

Use together

Useful next steps and companion tools, organized around the workflow.

Organize pages PDF Organizer Reorder or clean up pages before or after comparing PDFs. Scan paper Document Scanner Turn paper documents into PDFs first, then compare them. For photos Same Spot Diff Compare before/after photos of the same place with automatic alignment.