Compare two PDFs and find the differences
Drop in the old and the new version: every added, deleted or changed word is highlighted on the pages, and you jump from one change to the next in a click.
- Free
- Word by word
- Visual comparison
- 100% private
100% private — Everything is processed directly in your browser: your files, voice, and image are never sent to Chatzam's servers.
How to compare two PDF files
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Drop in both versions
Put the original document in A and the revised version in B, or drag both files in at once: the first one becomes A.
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Go through the differences
The number of changes shows up right away. Click a change in the list or “Next” to see it highlighted on both pages.
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Switch to visual mode if needed
For a drawing, a scan or a layout, overlay the pages: anything only in the original shows in red, anything new in blue.
Everything that changed, without reading anything twice
Word-by-word diff
The full text of both documents is compared: a sentence pushed onto the next page doesn't count as a difference, so only real changes stand out.
Highlights on the pages
Both documents are shown side by side, pages matched by content, with additions in green and deletions in red at the exact spot.
Visual comparison
Pixel differences in red and blue, or an overlay with an opacity slider: ideal for drawings, scans and mockups.
Nothing is uploaded
Both PDFs are read and compared in your browser. Your contracts and internal documents never leave your device.
Compare two versions of a contract without missing a thing
When a lease, an employment contract or terms and conditions come back “with a few edits”, rereading both versions line by line is slow and unreliable: a changed figure or an added “not” easily slips through. The tool extracts the text of both PDFs and compares them word by word. Each change is classified as an addition, a deletion or a modification, with the page number in each version and a few words of context. For example, if “one month's notice” becomes “three months' notice”, you see exactly those words struck through in red and replaced in green. You can then print or save as PDF a report listing every difference.
Why pages are matched by content
Adding a paragraph on page 2 shifts the rest of the document: page 5 of the original now matches page 6 of the new version. Comparing page 5 with page 5 would flag false differences everywhere. Here, the text of both documents is compared in one go, then pages are paired up according to the words they share. A page that was added or removed appears alone on its row, with a note saying so. In side-by-side view, a single scrollbar moves both documents together, and you can show only A or B to read in a larger size on a phone.
Text or visual: which mode should you use?
Text mode suits documents produced by a word processor or other software: contracts, reports, quotes, theses. It doesn't work on a scan, which only contains an image: in that case, the tool tells you and suggests Visual mode. Visual mode renders both pages and compares them pixel by pixel. Anything that appears only in the original shows in red, anything only in the new version in blue, and the rest fades to gray. The sensitivity slider ignores small variations caused by scanning; the overlay, with its opacity slider, lets you fade gradually from one version to the other, for example on an architect's drawing.
Frequently Asked Questions
How do I find the differences between two PDFs?
Drop in both files: the text is compared word by word automatically. The number of changes is displayed, each difference is highlighted on the pages, and the “Next” button takes you from one to the next.
Can I compare two scanned PDFs?
Yes, with Visual mode: the pages are overlaid and compared pixel by pixel. Text mode needs selectable text; for a scan, first make it searchable with a text recognition (OCR) tool.
What if the two documents don't have the same number of pages?
That's not a problem. Pages are matched by content: an added page appears on its own, marked “missing from A”, and text that moved from one page to another isn't counted as a difference.
Can I keep a record of the differences?
Yes. The “Print report” button opens a summary of every change, with the pages involved, which you can print or save as PDF from the print dialog.
Are my documents uploaded to a server?
No. Reading and comparing happen entirely in your browser: your PDFs are never uploaded, which makes it suitable for contracts and confidential documents.