Compare PDF Files Online — Free & Private
Drop two PDFs and see every change highlighted instantly. SnapTextCompare extracts text from each PDF locally in your browser and diffs it word by word — no upload, no signup, no fee. Built for legal, finance, academic and engineering teams that can't ship sensitive PDFs to a third-party server.
No comparison yet. Paste or upload text in both fields below — results appear here automatically, and nothing is calculated until you do.
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Why Compare PDFs in Your Browser?
Most PDF comparison tools — Diffchecker, Draftable, Adobe Acrobat — upload your PDF to a server before producing the diff. That's a non-starter when the file is a signed NDA, a confidential contract draft, an M&A term sheet, or a patent application. SnapTextCompare loads pdf.js inside your browser tab, extracts the text from each PDF, and runs the diff entirely client-side. The file never touches a network.
That also makes it fast: there's no upload step, no queue, no rate limit. Drop the file, see the diff.
PDF Comparison Use Cases
Legal redlines. Compare a draft and the counterparty's revised contract to verify only negotiated terms were touched.
Policy & compliance. Diff successive versions of a regulatory policy PDF to write a clean change log.
Academic papers. Compare a submitted and a revised manuscript to track reviewer-requested edits.
Engineering specs. Diff two versions of a datasheet, RFP or technical specification before quoting or shipping.
Financial reports. Compare two PDF financial statements to spot adjustments between drafts.
How It Works
1. Parse. Both PDFs are read with Mozilla's pdf.js, page by page, in the browser.
2. Tokenize. Extracted text is normalised and tokenised by word or by line.
3. Diff. A Myers-style diff algorithm computes additions and deletions.
4. Render. Results are highlighted inline — green for added, red for removed — with character-level precision on changed words.
Limitations & Tips
Scanned PDFs: Image-only PDFs need OCR first (try Tesseract or Adobe Acrobat's "Recognize Text"), then bring the text here.
Very large PDFs: Aim for under ~10 MB per file. Larger files work but consume more memory.
Layout changes: SnapTextCompare diffs the extracted text stream, not visual layout. For visual layout diffs use a graphical tool.
Related comparison tools
How SnapTextCompare compares PDF files
Diff engine
Google's diff-match-patch (Apache 2.0), running in your browser. Character mode diffs raw characters; word and line modes encode tokens or lines first and diff those, then decode the result.
Similarity & importance
Similarity = 1 − Levenshtein / max(len). Importance weighs each change by category — money and dates score 90+, punctuation scores 3. Deterministic on any device.
Privacy
Files are read with the HTML5 File API and processed in your browser. No network request is ever made with your content — verifiable in the Network tab of your browser's DevTools.
PDFs are parsed with Mozilla's pdf.js directly in your browser — page by page, text-layer only. Scanned/image PDFs need OCR first and are not currently supported. Font-embedded encoding quirks are normalised so ligatures (fi, fl) and soft hyphens don't appear as false differences.
PDF Comparison FAQ
Common questions about comparing PDF files online.