Compare two PDFs

Text differences side by side

No database: AIMRAN doesn't store your files, text or results

What is Compare two PDFs?

When you receive a new version of a contract, a quote or a paper, finding what has changed by reading both documents is slow and easy to miss. This tool does it for you.

You upload the original PDF and the new version, and see the added, removed and changed lines, with the exact words that changed highlighted. You can show only the changes to go straight to what matters.

How to use it

1. Add the original PDF as A and the new version as B.
2. Click “Compare”.
3. Choose the view: “Side by side” or “Unified”.
4. Turn on “Changes only”, “Ignore case” or “Ignore whitespace” if you need to.
5. Review the summary and, if you like, download the .diff file.

Advantages

• Highlights the exact words that change within each line.
• Side-by-side or unified view, with page markers.
• Summary of added, removed and changed lines.
• Export in standard .diff format.

Technical details

Text is extracted from both PDFs with pdf.js and compared line by line with the diff library (Myers algorithm), with optional normalization of case and whitespace. When a block of removed lines is followed by a block of added ones, they are paired and a second word-by-word diff is calculated to highlight only what changes. The summary counts added, removed and changed lines as well as added and removed words, and the result can be downloaded as a patch in unified diff format. The comparison is text only: it does not detect changes in formatting, images or layout, and scanned PDFs need OCR first. Each PDF can be up to 200 MB.

Frequently asked questions

How do I compare two PDFs to see the differences?

Add both files, click “Compare” and you will see added lines in green, removed lines in red and changed words highlighted.

Does it detect changes in images or formatting?

No. It compares text only. Changes in font, colors or images don't show up.

Can I compare scanned PDFs?

You first need to run them through OCR so they contain text. Then you can compare them.

How do I ignore unimportant changes?

Turn on “Ignore case” and “Ignore whitespace” so they don't count as differences.

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