Compare Two PDF Documents Online: Side-by-Side Diff Inspector
Compare the text of two PDFs line by line and see added, removed and changed lines with a real similarity percentage.
Compare Two PDFs
Extracts the text of both files and runs a real line-by-line diff with changed words highlighted.
Text-based PDF
Text-based PDF
What this tool does and who it is for
Pick two PDFs and the tool extracts the text from each, then runs a real line-by-line diff. You get counts of unchanged, changed, removed and added lines, a similarity percentage, and a side-by-side view with changed words highlighted.
The similarity figure is calculated: 2 times the unchanged lines divided by the total lines in both documents. The view stacks into one column on phones.
It compares text only, not images, fonts, layout or signatures. Scanned PDFs need OCR first. Both files stay in your browser.
Official Formula / Technical Standard
Real-World Worked Scenario
Comparing a 20-page agreement shows 94.2% similarity with 14 added clauses and 6 deleted lines highlighted.
When people use it
Contract versions
See which clauses, dates and dollar amounts changed between a draft and the revision you were sent.
Policy or handbook updates
Check what a new edition changed before you re-read the whole thing.
Confirming a re-export
Verify that a regenerated PDF has the same text as the original.
Notes for US users
- For leases, loan documents and employment agreements, small changes such as a fee or date matter. Read every highlighted line.
- If a document is under an NDA, a tool that never uploads the file, as this one does not, avoids sharing it with a third party.
- For legal redlines, ask the other side for a tracked-changes version too. This tool only sees extracted text.
Limits and what to double-check
- •Text only: changes in images, charts, formatting, or signatures are not detected.
- •A reflowed paragraph or different line breaks can show as changed lines even when the wording is the same.
- •Very different documents use an approximate alignment, and the page says so when that happens.
Expert Best Practices & Common Pitfalls
Recommended Best Practices
- •Run a comparison before signing any vendor contract that has undergone redlining.
Common Mistakes to Avoid
- •Comparing scanned documents without first ensuring both have OCR text layers.
Step-by-Step Instructions
Upload Revision A
Select the original version of your document.
Upload Revision B
Select the modified or updated version.
Run Comparison
Click 'Compare Revisions Side-by-Side'.
Inspect Report
Review similarity percentage and line differences.
Features & Security Architecture
- Side-by-Side Comparison: Inspect Revision A and Revision B in synchronized panels
- Diff Metrics: Calculates similarity percentage, added lines, and removed clauses
- Visual Difference Indicators: Highlight modifications clearly in green and red
- 100% Private: Proprietary contracts and technical revisions never leave your browser
Frequently Asked Questions
Is this safe for NDA-protected agreements?▼
Yes! Both documents are compared purely inside your browser memory with zero cloud transmission.
How is the similarity percentage calculated?▼
As twice the number of identical lines divided by the total number of lines in both files. A line edited in place counts as not matching, so a few small edits can lower the figure more than you expect.
Can it compare scanned PDFs?▼
Not directly. A scan has no text layer. Run each file through the PDF to Text (OCR) tool first, keeping in mind that OCR errors will show up as differences.
Does it show which words changed?▼
Yes. When a line is edited, the left side highlights removed words and the right side highlights added words.
Is it safe for confidential agreements?▼
Both files are read in your browser and are not uploaded. Your own company policy may still apply to how you handle them.
Why do I see changes when the text looks the same?▼
Different line breaks, hyphenation or spacing between exports can change how lines are split. Compare the highlighted words to judge whether the meaning actually differs.