How CatchDiff Works
Upload two PDFs — CatchDiff finds every change in seconds. Smart page matching, character-level diffs, OCR for scanned pages, and AI-powered summaries.
Upload Two PDFs
Drag and drop your original and updated PDF files. Files up to 500 MB supported — everything runs in the cloud.
Smart Page Matching
Our algorithm uses cosine similarity to match pages — even when pages are reordered, inserted, or deleted between versions.
Review & Export
See every change side-by-side with character-level highlights. Add notes, run OCR on scanned pages, get AI summaries, and export to PDF.
See It in Action
Watch how CatchDiff compares PDFs in real time.
How to use CatchDiff
More tutorials coming soon. Subscribe on YouTube
Key Features
Every added, removed, or changed character is highlighted in green or red — not just line-level changes.
Cosine similarity algorithm detects reordered, inserted, and deleted pages automatically.
View actual rendered PDF pages side-by-side with diff highlights overlaid directly on the document.
Image-based pages detected automatically. Run OCR in your browser — no data sent to servers.
Get a plain-English summary of all changes. Bring your own API key or use built-in AI on Pro.
Export to PDF or text with notes and AI summary included. Share reports with your team.
Add comments on any page pair. Notes are saved in-session and included in exported reports.
Download the desktop app for Windows, Mac, or Linux. Works fully offline — no data leaves your machine.
macOS Users: Opening CatchDiff for the First Time
The CatchDiff desktop app is not yet signed with an Apple Developer certificate. When you first open the .dmg file, macOS may show a warning: "CatchDiff cannot be opened because Apple cannot verify it."
To bypass this:
- 1. Right-click (or Control-click) on the CatchDiff app icon.
- 2. Select "Open" from the context menu.
- 3. In the dialog that appears, click "Open" again.
You only need to do this once — after the first launch, macOS will remember your choice and open CatchDiff normally. Alternatively, go to System Settings → Privacy & Security and click "Open Anyway" next to the CatchDiff message.
We are working on getting an Apple Developer certificate to remove this step in a future update.
Ready to Compare?
Try CatchDiff free — 30 comparisons per month, no sign-up required.