Which version is the latest? What changed between draft 3 and draft 4? Comparing two PDFs by eye is slow and error-prone — a moved paragraph or a changed number is easy to miss. A visual diff highlights every change for you, and you can run it privately in your browser.
Why compare PDFs?
- Track changes between document versions
- Review contracts for edits before signing
- Catch mistakes — spot an accidental deletion or a changed figure
- Verify that a "final" file matches what you approved
How it works
The Compare PDF tool renders each page of both files to an image with pdf.js and compares them pixel by pixel. It shows three panels — Original, Changed, and a Differences view where altered pixels are highlighted in red. It also reports what percentage of each page differs. Everything runs in your browser; neither file is uploaded.
Step-by-step
- Open the Compare PDF tool
- Add the original PDF on the left and the changed PDF on the right
- Step through pages with the Prev/Next buttons
- Watch the Differences panel — red marks every change
Visual comparison vs text comparison
This tool compares the visual appearance of each page, which is powerful because it catches everything at once: edited text, moved images, formatting shifts, and layout changes all show up as red pixels. A purely text-based diff would miss visual changes like a resized logo or a shifted table.
If you specifically want to diff text content rather than appearance, extract the text (for example with PDF to Word) and use the Text Diff tool.
Reading the results
- "Identical on this page" — no visual difference detected
- "X% of pixels differ" — the share of the page that changed; small edits show a low percentage
- "Page exists in only one document" — the two files have different page counts
Frequently asked questions
Are my PDFs uploaded? No. Both files are rendered and compared entirely in your browser.
Does it detect tiny changes? Yes — even a single changed character shows up as red pixels in the Differences panel.
What if the files have different lengths? You can still step through every page; pages present in only one file are flagged rather than diffed.
Is it free? Yes — no account, no watermark, no limits.
Related tools
- Text Diff — compare two blocks of text
- PDF to Image — export pages as images
- Merge PDF — combine PDFs into one