Compare PDFs
Upload two PDFs and get a pixel-level visual diff — side-by-side, overlay slider, or highlighted diff view.
100% in your browser — files never leave your device
Original
Revised
When you need to know exactly what changed
Contract revisions, regulatory filings, design proofs, technical documentation — any situation where you need to confirm that two versions of a PDF are either identical or understand precisely what differs. Text-based diff tools miss layout changes and image replacements. A trained eye misses subtle font or spacing shifts.
This tool renders both PDFs to images and computes a pixel-level diff, so it catches every visual difference regardless of whether it is text, an image, a border, or a spacing change. The overlay slider is particularly useful for layout comparisons — drag it back and forth to see exactly how the two versions align.
Both files are processed entirely in your browser. No content is sent to any server.
Frequently asked questions
How does the visual diff work?
Both PDFs are rendered to images page by page. The diff view subtracts pixel values between the original and revised images, highlighting changed pixels in red while dimming unchanged areas. This is a pixel-level visual comparison — it detects any visual difference including text changes, layout shifts, image replacements, and formatting changes.
Are the files uploaded to a server for comparison?
No. Both PDFs are rendered entirely in your browser using pdfjs-dist. No files are transmitted to any server. The comparison runs locally using canvas pixel math.
What is the overlay view?
The overlay view shows both versions superimposed, with a draggable slider to reveal the original on the left and the revised version on the right. It is useful for spotting layout and content shifts by sliding between the two versions.
What does the percentage badge mean?
The percentage shows what fraction of the page's pixels changed between the two versions. Under 1% is green (nearly identical), 1–5% is amber (minor changes), and above 5% is red (significant differences). The percentage is approximate and depends on rendering resolution.
Can I compare PDFs with different page counts?
Yes. Pages are compared by index — page 1 of the original against page 1 of the revised, and so on. If the documents have different page counts, the comparison covers the pages they share in common and notes the difference in total pages.