`); } function previewSideBySide(srcA, srcB, title){ const win = window.open('', '_blank'); const safeTitle = (title || 'Preview').replace(//g,'>'); win.document.write(` `); } compareBtn.addEventListener('click', compare); clearBtn.addEventListener('click', ()=>{ fileA=null; fileB=null; infoA.textContent='No file selected'; infoB.textContent='No file selected'; showAlert(''); compareBtn.disabled=true; resultArea.style.display='none'; pagesContainer.innerHTML=''; }); startOverBtn.addEventListener('click', ()=>{ clearBtn.click(); }); downloadAllBtn.addEventListener('click', ()=>{ const imgs = pagesContainer.querySelectorAll('.image-preview'); if (!imgs.length) { showAlert('No images to download', 'warning'); return; } imgs.forEach((img, idx) => setTimeout(()=> downloadImage(img.src, `compare-${idx+1}.png`), idx*400)); }); })();

Compare PDFs

Quickly compare two PDF documents and see visual differences highlighted in red.

Ideal for reviewing revisions, verifying exported reports, contracts, or any document where small layout changes matter.

Processing happens in your browser with pdf.js — fast, private, and watermark-free.

FAQs

Q: How are differences detected?

A: Pages are rendered to images and compared pixel-by-pixel with an adjustable tolerance to reduce noise from anti-aliasing.

Q: Can I compare PDFs with different page counts?

A: Yes. Missing pages are shown as blank, and you can still review the differences for pages that exist.

Q: Is my data uploaded?

A: No. The comparison runs locally in your browser using pdf.js, so files never leave your device.