Skip to content
Repair & OCR

Compare two PDF files, free

Drop the original and the revised version and see every word that was removed (red) or added (green) — listed with its page, marked on a side-by-side PDF of both. Compared in your browser; neither file is uploaded.

Compare PDFs

Settings appear once you add a PDF.

Advanced 2
Ignore capital letters “Buyer” and “buyer” count as the same word.
Ignore punctuation A moved comma or a straight quote turned curly isn’t reported as a change.

Bytes sent anywhere: 0 B

  • 100% private Your PDFs never leave this device. Everything runs in your browser.
  • No limits No file-size cap, no watermark, no sign-up and no daily quota. Free.
  • Batch ready Add as many PDFs as you like; each one is handled and saved in one go.

How to compare two PDF files

  1. Add your PDFs: Drop the original first and the revised version second. Swap them with the arrows if they’re the wrong way round.

  2. Check the settings: Press Compare. The text of both is read and matched word by word, so re-wrapped paragraphs aren’t reported as changes.

  3. Save the result: Read the list of changes, then save the side-by-side PDF — the original on the left, the revision on the right, every change highlighted — or the revised copy with its additions marked.

Why it doesn’t upload

The documents people compare are the ones mid-negotiation: a contract after the other side’s redlines, a lease, a policy before it is signed off. Both versions are read and compared in this browser tab, so neither draft sits on a comparison service’s server.

Check it in your browser’s Network tab

Worth knowing

  • Only the words are compared. A changed picture, color, font or layout that leaves the words alone isn’t reported.
  • Scanned PDFs have no text to compare. Run them through OCR PDF first — then OCR mistakes can show up as small differences.
  • The side-by-side PDF pairs pages by number. When a page was added or removed, the two sides drift apart from there on; the list of changes and the highlights are still exact.
  • Text the other side moved to a different place shows as removed in one spot and added in another, not as a move.
  • Very different versions — a rewrite rather than an edit — are marked in larger blocks rather than word by word, and the result says so.

Under the hood

What happens to your file

pdf.js reads the text of both files with each word’s position. Lines are compared first with Myers’ diff algorithm, then the words inside the lines that differ, so text that only re-wrapped matches and isn’t reported. Removed words are highlighted on the original and added words on the revision with pdf-lib, and both are placed side by side as vector pages, not pictures.

Runs on pdf.jspdf-lib

Reference: Myers, An O(ND) Difference Algorithm (1986) · pdf.js, Mozilla

Why compare two PDFs word by word?

When a contract comes back from the other side, reading both versions side by side to find what changed is slow and unreliable. A comparison lists every removed and added word with its page, and marks them on a side-by-side PDF, so nothing slips through.

Both versions are compared in your browser — a draft mid-negotiation isn’t uploaded to a comparison service.

Common reasons to find differences between PDF versions

  • Contract redlines

    See exactly what the other side changed before you sign.

  • Policy and terms updates

    Find what changed in a new version of terms or a policy.

  • Proofreading final versions

    Confirm only the agreed corrections were made.

  • Academic drafts

    See what changed between drafts of a paper or thesis.

  • Price lists and quotes

    Spot changed figures between two versions of a quote.

Tips for comparing PDFs

  1. Put the original first and the revised version second.
  2. Turn on Ignore punctuation if moved commas are noise.
  3. Scans need OCR PDF first; then small OCR slips can show as differences.
  4. When pages were inserted, the side-by-side view drifts, but the change list stays exact.
  5. Moved text shows as removed in one place and added in another.

Questions

How do I compare two PDF files for differences?

Drop both files here — the original first — and press Compare. You get a list of every change with its page number, a side-by-side PDF with removed words in red and added words in green, and the revised file with its additions marked.

Can I compare two versions of a contract without uploading them?

Yes. Both files are read and compared inside your browser tab; nothing is sent anywhere. You can check it in your browser’s network panel while it runs, or switch off Wi-Fi after the page loads.

Does it find changes in numbers and dates?

Yes. Every word counts, so net 30 becoming net 45 or 2026 becoming 2027 is listed like any other change. Turn on Ignore punctuation under Advanced if a moved comma is noise to you.

Why does a re-wrapped paragraph not show as changed?

Lines are only a first pass. Where lines differ, the words themselves are compared, so text that simply flowed onto different lines after an edit elsewhere matches word for word and isn’t reported.

Can it compare scanned PDFs?

Not directly, because a scan is a picture of words. Make both searchable with OCR PDF first; the comparison then works on the recognized text.

Read more about this

More repair & ocr tools

All repair & ocr tools