PDF Tools
Compare PDF Files Online
Find selectable-text, image, layout, and page differences without uploading either PDF.
PDF A
Drop or browse for the first PDF
PDF A stays on your device.
PDF B
Drop or browse for the second PDF
PDF B stays on your device.
How this PDF difference checker works
FiloTool pairs page 1 with page 1, page 2 with page 2, and so on. It extracts selectable text with PDF.js, normalizes line endings and repeated horizontal whitespace, and reports added or removed lines. It also renders matching pages at an aligned, controlled resolution and compares their pixels, so image, layout, formatting, and scanned-page changes remain detectable.
Visual comparison thresholds and limits
A pixel is materially different when an RGB channel differs by more than 24 levels. A matching page is visually changed when at least 0.1% of its aligned rendered pixels are materially different. This tolerance reduces anti-aliasing noise but does not make the result pixel-perfect or semantic. Each PDF can be up to 40 MiB and 120 pages; actual capacity depends on device memory and page complexity.
Privacy and practical limitations
PDF and rendered-page bytes remain in your browser and are released as the comparison advances. Detailed previews are rendered only for the selected page. Password-protected files must be unlocked first. Phase 1 compares source indexes and does not detect page reordering, perform OCR, or claim legal-grade document comparison.
Checking a redaction
Comparing an original PDF against a redacted copy shows exactly which pages changed and highlights any text that unexpectedly remains. Use Redact PDF to produce the flattened copy, then compare it here before sharing.
Frequently asked questions
Are my PDFs uploaded?
No. Both PDFs stay on your device. FiloTool uses PDF.js and browser canvases to compare them without sending PDF bytes or rendered pages to a server.
Can it compare scanned PDFs?
Yes. Scanned or image-only pages can be compared visually without OCR. Text-change details require meaningful selectable text in both matching pages.
What happens when page counts differ?
Pages are paired by source index. Extra pages in PDF B are marked added; extra pages in PDF A are marked removed. This version does not detect reordered pages.
Is this a legal-grade comparison?
No. The tool reports normalized selectable-text changes and materially different rendered pixels. It does not establish semantic or legal equivalence.