pdfcosmos

Compare PDF

Compare two PDFs and see exactly which lines were added or removed.

Free, fast, and privacy-first.

Add the original PDF

The first version. You'll add the revised copy next

or drag & drop a PDF here

PDF files only · two files · up to 100 MB each

Compare two PDFs and see exactly what changed

Find the differences between two versions of a PDF (a contract, a policy, a draft) without reading them side by side. pdfcosmos lines up the text of both documents and highlights every added and removed line, entirely in your browser, so neither file ever leaves your device.

It offers two modes. Text mode reads each PDF's own text layer (full Unicode) and runs a line-level diff, showing additions and removals and letting you download an HTML report of the changes. It doesn't look at layout, images, or formatting, and scanned (image-only) PDFs have no text to compare, so you'll get a clear message rather than an empty report. Visual mode overlays the two files page by page and highlights the changed pixels in red. It catches moved images, colour changes, and layout shifts, and works on scans too.

  • See every text change

    Added and removed lines are highlighted in document order (down to the exact words that changed) with a count of each.

  • Download a report

    Save a self-contained HTML report of the differences to keep or share.

  • Honest about scope

    A text compare (not layout or images), and scanned PDFs are flagged as needing OCR.

  • Nothing is uploaded

    Both PDFs are read and compared in your browser. They never leave your device.

How to compare two PDFs

  1. Add both PDFs

    Choose the original PDF, then the revised copy you want to compare it against.

  2. Compare

    Click “Compare PDFs”. Both files are read in your browser and their text is lined up.

  3. Review and download

    See every added and removed line highlighted, and download an HTML report of the changes.

Frequently asked questions

Are my PDF files uploaded to a server?
No. Both PDFs are read and compared entirely in your browser using pdf.js. Your files never leave your device. You can confirm it in your browser's Network tab: no file data is sent.
What does it compare?
The selectable TEXT of the two documents, line by line. It highlights every added and removed line, and within a changed line it highlights the exact words that differ. It's ideal for spotting wording changes between two versions of a contract, policy, or draft.
Does it compare layout, images, or formatting?
Yes. Switch from Text to Visual mode. Text mode compares wording only, so it won't flag a moved image, a colour change, or a reflowed layout that leaves the words the same. Visual mode overlays each page and highlights the changed pixels in red, so it catches all of those (and works on scans too). Visual mode compares a limited number of pages per run, and a page-size difference shows up as a changed region.
Does it work on scanned PDFs?
No. Scanned pages are images with no text layer, so there's nothing to compare (that would need OCR). If neither PDF has selectable text, you'll get a clear message instead of an empty report.
Which languages and characters are supported?
Any text stored in the PDFs' text layers, including non-Latin scripts like Arabic or Chinese. Comparison is full Unicode, and the downloaded report is saved as UTF-8 HTML.
Is Compare PDF free?
Yes, it's completely free to use, with no sign-up and nothing to install.