PDF Compare

Pixel-Level Precision with DELTA-E Algorithm

The PDF Compare tool is a browser-based utility that compares two PDF files page by page at the pixel level, highlighting differences in red. Rather than using simple color subtraction, it employs the DELTA-E 76 algorithm defined by the International Commission on Illumination (CIE), enabling color difference detection that closely mimics human visual perception. This approach accurately detects even subtle color shifts and fine contrast variations.

Versatile Applications

It is ideal for reviewing revised contracts, specifications, and reports, verifying design corrections, checking translation differences, and pre-press proofreading. The tool displays the difference ratio as a percentage, allowing you to quantitatively assess the magnitude of changes at a glance.

Flexible Sensitivity Adjustment and Three-Pane View

A sensitivity threshold slider lets you adjust detection precision on the fly—ignore minor rendering artifacts or catch even slight color shifts depending on your needs. The default value (DELTA-E 15) detects both subtle and significant changes. As a guideline: DELTA-E below 2 indicates visually equivalent colors, 5–15 represents subtle differences, and 15–30 indicates distinct changes.

Maximum Security and Privacy

All processing happens entirely in your browser; PDF files are never uploaded to any server, ensuring complete confidentiality for sensitive documents, contracts, and personal information. You maintain full control over your data at all times.

Multi-Page Support

A page navigation feature allows efficient comparison of multi-page PDFs. The tool handles PDFs with different page counts gracefully, automatically graying out pages that do not exist in one document.