Drop two versions of a contract, report or paper to see what changed. Diffspot extracts the text of each PDF in your browser (using Mozilla's pdf.js) and compares it word by word. The redline view reads like tracked changes, and side by side shows the two versions in parallel. Nothing is uploaded, which matters for legal and financial documents.
How to compare two PDFs
- Drop the original PDF on the left (or click Open).
- Drop the revised PDF on the right. Text is extracted page by page on your device.
- Read the redline with deletions struck through and insertions underlined, or switch to side by side.
- Save the result with Export → Print / save as PDF or Download HTML report.
Why Diffspot
- Confidential by designPDFs are opened locally. No upload, no conversion server, no copies kept anywhere.
- Word-level redlineChanges are shown word by word, like tracked changes in a word processor.
- Pages markedPage breaks are kept as markers so you can find each change in the original document.
- Shareable reportExport a self-contained HTML report or print to PDF for your records.
- Fast on big inputsThe diff engine is written in Rust and runs in a background thread, so typing stays smooth. Files with hundreds of thousands of lines compare in about a second.
- Free, no accountEvery feature is free with no sign-up and no size paywall. Ads pay for the site, and they run in an isolated frame that can't read the page.
Frequently asked questions
Does it compare scanned PDFs?
Only PDFs with a text layer can be compared. Scanned pages are images; run them through OCR first (many scanners and PDF apps can do this).
Does it compare layout, images or formatting?
No. Diffspot compares the text. For visual changes, export pages as images and use the image comparison.
Why do some lines break differently?
PDFs store text as positioned fragments. Diffspot rebuilds lines and joins hyphenated words, but unusual layouts like multiple columns can produce different line breaks on each side. The redline view is the most forgiving for this.
Is it safe to paste confidential text or files?
Yes. Diffspot computes every comparison on your device: the page loads the engine once, then your text and files stay in the browser tab. There is no upload and no server-side storage, and ads are shown in a separate sandboxed frame that cannot read the page. How Diffspot works explains the details, and you can confirm it in your browser's network panel.
Is Diffspot free?
Yes. All features are free, with no account, no trial and no limit on the number of comparisons. The site is supported by ads, which never see what you compare.