How are pages paired?

By 1-based page index. If the two PDFs have different page counts, the missing side renders as white (so the diff is the entire page).

How sensitive is the diff threshold?

Pixels with combined RGB delta above 30 are flagged red. That tolerates JPEG-recompression artifacts and minor anti-aliasing differences.

Are the files uploaded?

No — rasterisation and diff happen in your browser.

Visual Diff (Image-based)

Compare two PDFs visually — rasterise each page, overlay the two as red/green channels, and produce a PDF that highlights pixel differences.

Your files never leave your browser. All processing happens on your device — nothing is uploaded.

1. Upload your files (min 2)

Need at least 2 files (have 0).

How does the Visual Diff (Image-based) work?

Compare two PDFs at the pixel level. Each page from both files is rasterised at 1.5×, the pixel values are diffed, and the result is a new PDF where every page shows where the two differ (red pixels) on top of a faint grey rendering of the older version. Different from text-based comparison (Compare Two PDFs / Redline Comparison) — visual diff catches anything: text, images, layout shifts, stamp positions. Useful for proof-reading layouts where the text is identical but something visual moved.

🔒 Security & Privacy

All processing happens on your device. Your files never leave your browser, never touch our servers, and are not stored anywhere. Close the tab and the file is gone.

📱 Use it on any device

Works in any modern browser — Mac, Windows, Linux, iPhone, Android, and tablets. No installation, no app to download. Just open the page and start.

⚡ Quick & easy

Drag, drop, click. Most files process in seconds, not minutes. No watermarks added to your output, no per-day limits, and the tool always shows the result before asking you to download.

🎁 Always free, no signup

Free to use, every time. No account creation, no email required, no “trial” that converts to a paid plan. We make money from ads so you don’t have to pay.

Frequently asked

Text diff (Compare Two PDFs, Redline Comparison) only catches changes in extracted text. Visual diff catches everything visible — stamps, image swaps, font substitutions, layout shifts.