VSThiran

PDF & Files

Compare Two PDFs and See What Changed

Free to useNo sign-up requiredNo watermarkRuns in your browser

This compares two PDFs the way a proper diff tool compares two versions of a document: it pulls the text out of each one and shows you exactly which lines were added, which were removed, and which are unchanged, side by side.

It reuses the same text extraction PDF to Word, PDF to Excel and PDF to Text already use, and the same line-matching engine as Text Diff Checker - a PDF-to-PDF comparison is really "extract both, then diff the text," not a separate comparison method of its own.

How this tool works

  1. Add PDF A

    The original, or the older version.

  2. Add PDF B

    The changed, or the newer version.

  3. Read the differences

    Every line is matched between the two documents - green for added, red for removed, plain for unchanged.

  4. Copy or download

    Copy the comparison directly, or download it as a plain-text diff.

How it works

Each PDF is read in your browser and its text extracted in reading order - the same extraction the PDF to Word, PDF to Excel and PDF to Text converters use, which groups text into lines by position on the page.

The two resulting texts are then compared line by line using the shortest-edit-script method version control systems use, so lines that only moved (rather than changed) are recognised as unchanged, and only genuine differences are marked.

Only text is compared. Formatting, fonts, colours, images and exact page layout are not part of the comparison, because neither PDF's extracted text carries them - two visually different PDFs with identical wording will show as identical here.

What this does and does not catch

This is a text comparison, not a visual one. It is built for catching wording changes - a clause reworded in a contract, a figure updated in a report, a paragraph added or removed - not for spotting a logo moved half an inch or a colour changed.

  • Catches: added, removed or reworded text, anywhere in the document.
  • Catches: text that moved to a different page, if the wording itself is unchanged.
  • Does not catch: formatting, font, colour or layout changes with identical wording.
  • Does not catch: differences in images, unless you also compare their surrounding text.
  • Cannot compare: a scanned PDF with no real text - run OCR on it first.

Why not just look at both PDFs side by side?

For a one-page document, eyeballing both usually works. For a multi-page contract, report or manual, small wording changes are easy to miss by reading alone - a single word changed in a ten-page agreement is exactly what this is for.

Worked examples

Two drafts of a contract

See every clause that was added, removed or reworded between versions, without reading both drafts side by side.

A report re-issued with corrections

Confirm exactly which figures or paragraphs changed in the corrected version.

A policy document updated annually

Check what actually changed from last year's version before you read it in full.

Frequently asked questions

Is this PDF comparison tool free?

Yes - free, no sign-up, no watermark and no limit on how many times you use it.

Are my files uploaded to a server?

No. Your files never leave your device. The file is opened and processed by your browser on your own machine, so nothing is transmitted to VSThiran and no copy of your document is ever stored on a server.

Does this compare formatting and layout, or just text?

Just the text. Two PDFs with identical wording but different formatting, fonts or colours will show as identical, because the comparison is based on extracted text, not on how the page is drawn.

Can I compare scanned PDFs?

Not directly - a scan has no real text to extract. Run the OCR workspace on each scan first, then compare the recognised text using the Text Diff Checker, or re-run this tool once both are text-based.

What do the added and removed counts mean?

"Added" is the number of lines present only in PDF B (the changed one); "removed" is the number present only in PDF A (the original). Lines present in both, in the same position in the sequence, count as unchanged.

Will reordering pages show as a huge diff?

Not necessarily. The comparison matches on text content, not page number, so a paragraph that moved to a different page but was not reworded is still recognised as unchanged.