Compare PDFs Online Free — Text Diff Tool
Compare two PDF documents side by side and see exactly what changed. Extract text from both files and highlight added, removed, and unchanged content. All processing stays in your browser.
PDF A (original)
PDF B (revised)
Summary
Text Differences
The two PDFs appear to have identical text content.
How to Compare Two PDFs Online
Upload two PDF files and instantly see every text difference — word by word. No installs, no uploads, no signup. Both files stay on your device the entire time.
- Upload PDF A — the original version of your document.
- Upload PDF B — the revised or updated version.
- Click "Compare PDFs" — the tool extracts text from both files and highlights every difference: green for additions and red strikethrough for removals.
When to Compare PDFs
- Contract review — spot changes between contract versions, redlines, or amendments.
- Legal documents — compare filings, agreements, or terms for unauthorized modifications.
- Academic papers — track revisions between drafts of your thesis or manuscript.
- Policy documents — verify what changed in updated terms of service or privacy policies.
- Resume versions — check differences between your tailored resume versions.
- Regulatory filings — compare annual reports or compliance documents across periods.
How the Comparison Works
The tool extracts selectable text from both PDFs using pdf.js and runs a word-level diff algorithm. It identifies words that were added, removed, or kept the same between the two versions. A similarity percentage gives you a quick overview of how much changed.
Limitations
- Text only — this tool compares text content, not visual layout, images, fonts, or formatting.
- Scanned PDFs — PDFs that contain only images (no text layer) cannot be compared. Use our PDF OCR tool first to extract text, then compare the results.
- Word-level diff — the comparison is word-by-word. It does not perform semantic or structural comparison.
- Large documents — very large PDFs (>100 pages) may be slow. Consider splitting into smaller sections for comparison.
Privacy & Security
Both PDF files never leave your device. Text extraction and diff computation happen entirely in your browser using JavaScript. We do not upload, store, or analyze your files. No server processing, no third-party access.
FAQ
Will my PDF files be uploaded to a server?
No. All processing — text extraction and comparison — happens in your browser using JavaScript. Both PDF files stay on your device. We cannot see or access your documents.
What exactly is compared?
The tool extracts selectable text from both PDFs and performs a word-by-word diff. It identifies which words were added, removed, or stayed the same between the two versions. Visual elements like images, fonts, and page layout are not compared.
Can it compare scanned PDFs?
Only if the scanned PDF has been OCR'd and contains a text layer. If your PDF contains only images without selectable text, use the PDF OCR tool first to extract the text, then compare the extracted text files.
How accurate is the comparison?
The word-level diff algorithm is deterministic and accurate for text content. The similarity percentage is based on word counts. Two PDFs with identical text but different formatting will show 100% similarity.
Are formatting changes detected?
No. The tool compares only text content. Changes to fonts, colors, spacing, margins, images, or page layout are not reflected in the comparison.
What's the file size limit?
Files up to 50 MB work reliably in most browsers. Large PDFs with many pages may take longer to process. Both files and their extracted text must fit in browser memory.
Can I compare more than two PDFs?
This tool compares exactly two PDFs at a time. To compare multiple versions, run pairwise comparisons: A vs B, then B vs C, and so on.
Does this work on mobile?
Yes, the comparison works on mobile browsers. However, the diff view is easier to read on larger screens. Large PDFs may be slower on mobile devices.