Your Contract/PDF Redline Diff Viewer
Free redline diff checker. Upload two versions of a PDF, .docx or .txt document and see every addition in green and every deletion struck through in red.
- Free to use
- No signup
- Nothing to install
- Runs in your browser
Your inputA real example, step by step
Real data entered into the Contract/PDF Redline Diff Viewer, one screenshot per step. Nothing is mocked up.
- 1
Open the tool
The Contract/PDF Redline Diff Viewer opens ready to use, nothing to install or sign up for.
- 2
Add your file
Choose a file, here sample.pdf, and the Contract/PDF Redline Diff Viewer reads it straight in your browser tab.
- 3
Press Compare and show
The Contract/PDF Redline Diff Viewer shows the result straight away, below the same form.
What is the Contract/PDF Redline Diff Viewer?
When a contract, policy or report goes through several drafts, finding exactly what changed between two versions by eye is slow and risky — a single deleted clause or changed number is easy to miss. This tool takes two documents, the original and the revised version, extracts their text and shows a redline: every word that was added appears highlighted in green, and every word that was removed appears struck through in red, exactly like the markup a lawyer or editor would produce by hand.
It accepts PDF, plain text (.txt) and Word (.docx) files in any combination — extracting PDF text with pdf.js and .docx text with mammoth.js, the same libraries already used elsewhere on this site. The comparison itself runs a word-level (or, if you prefer, line-level) diff algorithm entirely in your browser, so contracts and sensitive documents never leave your device. A summary shows how many words were added, how many were removed, and an overall similarity percentage, so you can gauge at a glance how heavily a document was revised before reading the detail.
3 steps to your result
Open the tool and follow along. Nothing to install.
What you get
Extracts text locally with pdf.js and mammoth.js.
Switch modes depending on how granular you need the comparison.
Green additions, red strikethrough deletions — familiar to anyone who has reviewed tracked changes.
Words added, words removed and an overall similarity score.
AZRS tools are free to open and use.
It opens in your browser, so there is nothing to download.
Used for
Pick one to see how it fits.
Lawyers and paralegals
Spot every change between contract drafts without reading both versions side by side.
Try it freeProcurement and compliance teams
Compare policy or terms-of-service revisions quickly.
Try it freeHow it compares
A plain look at this tool next to the usual alternative.
| This utility | Desktop software | |
|---|---|---|
| Install | Nothing to install | Usually an app or program to install |
| Account | No signup | Depends on the product |
| Cost | Free to use | Free or paid, depends on the product |
| Where it runs | In your browser tab | On your computer |
Questions people ask
Does this tool store or upload my documents?
No. Text extraction and comparison both happen in your browser using pdf.js and mammoth.js; your files are never sent to a server.
Can it compare a PDF to a Word document?
Yes — you can mix formats freely; each file's text is extracted independently before comparing.
Why does a scanned PDF show no differences or empty text?
Scanned PDFs are images with no embedded text layer, so pdf.js cannot extract words from them. Use an OCR tool first, or compare the text-based source files instead.
What is the similarity percentage?
The share of matched words in the diff versus the total words compared — a rough indicator of how much changed, not a legal measure of similarity.
Is there a size limit?
Very long documents (tens of thousands of words) automatically switch to a faster block-comparison mode to stay responsive; for typical contracts and reports the full word-level diff runs in seconds.
More free tools
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Try the Contract/PDF Redline Diff Viewer now
Compare two PDF, text or Word documents and see a redline of every change. Free to use.
Try it free