Free PDF Compare — Diff Two PDFs Page by Page Online
Spot what changed between two versions of a document. Upload PDF A and PDF B, and this tool extracts the text of every page with pdf.js, scores each page pair for similarity, highlights the changed pages, and shows side-by-side diffs for the pages you pick. Everything runs in your browser; files never leave your device.
Compare Two PDFs
Page-by-page text diff with similarity scores — find exactly what changed.
1 Add both PDFs
2 Comparison options
3 Compare
📊 Comparison report
How it works
Each PDF is rendered page-by-page with pdf.js (Mozilla’s JavaScript PDF engine), which extracts the embedded text layer. Lines are reconstructed from text items, then normalized per your settings (whitespace collapsing, case folding). Each page pair gets a similarity score using word-overlap math (shared words ÷ total unique words × 100). Pages below your threshold are flagged, and clicking one shows a side-by-side diff: matching lines at the top and bottom are aligned, the changed middle is highlighted red (removed) and green (added).
Honest limitations: only extractable text is compared — scanned images with no text layer compare as empty (run OCR first), and layout, fonts, colors, and images are ignored. Two pages can look different but score 100% if their text matches.
Everyday uses
- Contract review — diff the redlined version against the original before signing.
- Legal teams — prove exactly which clauses changed between drafts.
- Editors — verify a “final” PDF matches the approved manuscript text.
- Students — compare your exported assignment against the draft to catch missing pages.
- Compliance — document what changed between policy versions, page by page.