Files are processed in your browser, not uploaded. Privacy →
Deckle
Open a PDF

Compare PDF

Beta

Compare two PDFs page by page and see which areas look different and which pages' text has changed.

How to compare two PDF files

  1. Add the two PDFs you want to compare.
  2. Choose which file is the Before PDF and which is the After PDF.
  3. For each before page, choose the matching after page, or Deleted after if it was removed.
  4. Confirm any after pages left unpaired as insertions.
  5. Press Compare PDFs, then review the marked pages and download the report.

Options

Before PDF and After PDF
Pick the older and newer version. They must be two different files.
Page pairing
Each before page gets one after page or Deleted after. Each after page can be used once, so moved and reordered pages are paired by you rather than guessed.
Unpaired after pages
After pages with no partner are listed as inserted. Tick the box to confirm that before comparing.
Preview selected pages
Shows the chosen before and after pages side by side so you can check a pairing before you commit to it.
Undo, Redo and Reset
Step through or clear your file choices and pairings.

What you get

  • An on-screen report with changed areas outlined in red on each paired page.
  • A JSON report file, pdf-comparison-report.json, listing paired, deleted and inserted pages, changed pixels and whether the selectable text differs.
  • Neither PDF is changed, and no merged or marked-up PDF is produced.

Limits

  • Exactly two PDFs, up to 100 pages each.
  • Pages are compared as 512 px renders. Small, faint or very fine changes can be missed.
  • Up to 64 changed areas are outlined per page, and an outline can include unchanged pixels around a change.
  • Text is compared only where it is selectable, up to 20,000 characters per page. Scanned pages get a visual comparison only. No OCR is run.
  • The report shows where pixels differ, not which words changed. It is a review aid, not a legal or audit record.
  • Password-protected PDFs must be unlocked first.

Check the result

Open both PDFs at the pages the report marks and look at each outlined area. Deckle reopens the saved JSON and checks its page list and totals against your pairing; it does not recompute the differences.

Questions

Does it show which words changed?

No. It marks areas where the rendered page looks different and states whether the page's selectable text differs. Read the outlined areas to see the actual edit.

Why do I have to pair pages myself?

Pages are often added, removed or moved between versions. Pairing them yourself means each before page is compared with the page you know it became, not a guess.

Can I compare scanned PDFs?

Yes, visually. Scanned pages have no selectable text, so the report marks them as having no text to compare.

Is there a page limit?

Yes. Each PDF can have up to 100 pages.

Why are unchanged pages marked as different?

Differences in page size, crop, rotation or rendering show up as changed pixels even when the content is the same. Check those pages by eye.

Can I compare a page that moved to a different position?

Yes. Pair the before page with whichever after page it became, for example before page 3 with after page 7. The comparison follows your pairing, not page numbers.

Are my PDFs uploaded to compare them?

No. Both files are rendered and compared in your browser.

Related tools