Compare Two PDFs
Drop in two PDFs, see their text content compared line by line, with additions and removals highlighted.
Click or drop the original PDF
Click or drop the changed PDF
Drop in both PDFs to see the comparison.
How it works
Each PDF is read with pdf.js, the same engine Firefox uses to render PDFs, walking every
page's content stream to collect its embedded text via getTextContent(). The
two resulting texts are then split into lines and run through the same longest-common-
subsequence diff algorithm behind norito's Text Diff tool,
which finds the smallest set of line additions and removals that explains the difference
between the two documents, rather than naively comparing line-by-line position (which
would flag every line as changed after a single inserted paragraph).
As with any PDF text extraction, results depend on the PDF actually containing text. Scanned pages are images and contribute nothing to compare. Everything, extraction and diffing, runs in this browser tab; neither file is uploaded.
Common questions
Does this compare layout/design or just text?
Just text content. It extracts each PDF's embedded text and diffs that, so it catches wording changes, added/removed paragraphs, and edited numbers, but not visual-only changes like a font swap or a moved image with identical surrounding text.
Will this work on scanned PDFs?
No, scanned pages are images with no embedded text, so there's nothing to extract or compare unless the PDF was already run through OCR.
Are my PDFs uploaded anywhere?
No. Both files are read and compared entirely in your browser. Nothing is uploaded, which matters for contracts or drafts you're comparing.