Legal Document Comparison Tool

Drop two contract or legal PDFs to instantly compare them. Additions appear in green, deletions in red strikethrough. Generates a redlined PDF you can download — 100% client-side, your documents never leave your device.

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Original (v1)

Click or drag the original PDF here

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Revised (v2)

Click or drag the revised PDF here

How it works

This tool extracts the text layer from both PDFs, breaks them into paragraphs, then runs a word-level diff to pinpoint every change — no server, no data leaving your browser.

1. Text extractionPDF.js reads each PDF in your browser and extracts the full text layer, page by page, preserving paragraph breaks.

2. Diff analysisdiff-match-patch compares the two texts at word level and identifies every insertion, deletion, and unchanged run.

3. Redline displayDeletions are shown in red strikethrough, additions in green. A sidebar lists every changed paragraph for quick navigation.

4. PDF exportpdf-lib generates a new PDF with the full redlined text embedded as selectable text, ready to share with counsel.

Privacy note: Your PDFs are processed entirely in your browser using JavaScript. No bytes are transmitted to any server. Close the tab and all data is gone.

Frequently asked questions

What types of documents work best with this tool?: Any PDF that contains a selectable text layer: contracts, NDAs, service agreements, employment agreements, lease agreements, term sheets, amendments, and similar legal documents. Scanned PDFs without OCR (image-only PDFs) cannot be compared because there is no embedded text — you would need to run OCR first. Most PDFs created from Word, Google Docs, or any modern word processor will have a text layer and will work correctly.
Is my contract data safe? Does anything get uploaded?: Nothing is uploaded anywhere. The entire comparison runs inside your web browser using JavaScript. Your PDFs are read locally from your disk, processed in memory, and never transmitted over the network. You can disconnect from the internet after the page loads and the tool will still work. This is especially important for confidential legal documents — your data stays on your device at all times.
Why does my PDF show no changes when I know there are changes?: This usually means the PDF is a scanned image rather than a text-based PDF. Open the PDF in a viewer and try to select text with your cursor — if you cannot select any text, the PDF is image-only and needs OCR first. You can use our Bulk OCR PDF tool to add a text layer before comparing. Another cause is heavily reformatted documents where paragraph order has changed significantly; the diff algorithm will still catch the changes but may show more false positives.
How is this different from comparing in Microsoft Word?: Word's compare feature only works if you have both documents as .docx files. This tool works directly on PDFs — the native format you receive from counterparties, courts, and e-signature platforms. There is no need to convert formats, install software, or have a Microsoft 365 subscription. The result is also shareable as a standalone redlined PDF that any PDF viewer can open.
Can I compare documents longer than 50 pages?: Yes. The tool handles large documents in the browser, though extraction time scales with page count — a 100-page contract may take 10–20 seconds. The diff engine uses an efficient algorithm (Myers diff) that performs well even on lengthy documents. If the browser slows down, try refreshing and using the tool on a desktop machine with more RAM.