Free PDF Compare Online
Compare two PDF files side by side with visual difference highlighting. Instant results, no upload to any server.
Supports PDF files · up to 100 MB
Supports PDF files · up to 100 MB
How It Works
- Upload your first PDF by selecting or dragging it into the left drop zone.
- Upload your second PDF into the right drop zone.
- Choose your viewing mode: "Side by Side" displays both PDFs together, "Overlay" shows differences highlighted in red.
- Navigate through pages using the Previous/Next buttons or by entering a page number directly.
- In overlay mode, red highlights indicate pixel differences between the same page numbers in both documents.
Why Compare PDFs?
PDF comparison is essential for version control, quality assurance, and document management. Use it to track changes between document revisions, verify that edits were applied correctly, identify unauthorized modifications, compare contract or legal document versions, validate form submissions, and ensure document consistency across multiple copies. Automated difference highlighting saves time and reduces errors compared to manual review.
View Modes Explained
- Side by Side · View both PDFs simultaneously on the same screen. Ideal for spotting obvious layout changes, additions, or deletions. Both PDFs navigate independently.
- Overlay · Layers the second PDF over the first and highlights all pixel differences in red. Perfect for detailed change detection. Both PDFs must have the same page count for comparison.
Use Cases
- Version Control · Track changes between document versions and identify what was modified.
- Legal & Contracts · Compare contract versions to ensure all amendments were applied correctly.
- Compliance · Verify that forms and reports match approved templates or previous versions.
- Quality Assurance · Validate that generated documents match expected outputs.
- Fraud Detection · Identify unauthorized modifications or tampering in PDFs.
Frequently Asked Questions
How does overlay mode highlight differences?
Overlay mode performs a pixel-by-pixel comparison of the rendered pages. Any pixel that differs between the two PDFs is highlighted in red. This catches text changes, image modifications, spacing adjustments, and any other visual differences.
Can I compare PDFs with different dimensions?
Yes. PDFs with different page sizes are fully supported. In side-by-side mode, each PDF renders at its native size. In overlay mode, the first PDF determines the canvas dimensions.
What about scanned or image-based PDFs?
Scanned PDFs (composed of raster images) are fully supported. The comparison works by rendering both PDFs and comparing the visual output, so it detects changes in scanned documents just like any other PDF.
Can I compare encrypted PDFs?
This tool works with standard PDFs. If your PDFs are password-protected or encrypted, you'll need to remove the protection first using a PDF unlocking tool before you can compare them.
How large can my PDFs be?
Each PDF can be up to 100 MB. Processing time depends on file size, page count, and your device specifications. Very large files may take several seconds to load and render.
Is the comparison 100% accurate?
Yes, for visual differences. The tool performs exact pixel-by-pixel comparison, so it will detect any visual change. However, it compares rendered output, not underlying PDF structure—minor rendering differences due to fonts or PDF libraries might appear as differences when the actual content is identical.