Compare PDFs
Upload two PDFs and instantly see exactly which lines of text were added, removed, or unchanged — with word-level highlighting and a choice of unified or side-by-side view.
How to Compare Two PDFs
- Upload the original PDF into the first box, and the changed/updated version into the second box.
- Click "Compare PDFs" once both files are loaded.
- Review the line-by-line diff — green lines were added in the second file, red lines were removed from the first, and everything else is unchanged. When a line was edited rather than fully added or removed, only the changed words inside it are highlighted.
- Switch between "Unified" (one interleaved list) and "Side-by-side" (two aligned columns) using the view toggle.
- Check the stats row for a quick added/removed/changed/unchanged line count.
Frequently Asked Questions
What exactly gets compared — the text or the visual layout?
Just the text. Each PDF's text is extracted page by page (with a "--- Page N ---" marker between them) and compared line by line, so this tool won't catch changes to fonts, colors, images, or layout — only differences in the actual words.
Why does it say these PDFs are "too large to compare"?
The comparison algorithm's cost grows with the product of both documents' line counts, and the tool stops itself once that product passes 4 million to avoid freezing your browser. This typically only happens with very long documents on both sides at once.
Will formatting differences like an extra space or line break show as changes?
Possibly. Since text is extracted per page and joined by spaces, a paragraph that reflows differently between two PDF versions can shift where line breaks land, which may show up as several lines marked added/removed even if the actual wording didn't change.
Can I compare a scanned PDF to a text-based PDF?
Only if both have a real text layer to extract from. A scanned page with no underlying text will contribute an empty string for that page, so genuine content differences on that page won't be detected.
Does the diff show which page a change happened on?
Yes — each page's extracted text is preceded by a "--- Page N ---" marker line, so added/removed markers around that line indicate roughly where in the document the changes fall.
Can I see word-level changes within a modified line, not just the whole line?
Yes — whenever a block of removed lines is immediately followed by the same number of added lines (a 1-for-1 edit rather than a pure insertion or deletion), the tool runs a second word-level comparison on each matched pair and highlights only the words that actually changed, instead of marking the entire line. If the counts don't match, it falls back to whole-line highlighting since there's no reliable way to pair the lines up.
What's the difference between Unified and Side-by-side view?
Unified view shows one running list of lines with +/− markers, interleaving removed and added lines in document order. Side-by-side view splits the same diff into two aligned columns — the original on the left, the changed version on the right — which can be easier to scan when a lot of text moved around.