Odiff is a native, SIMD‑optimized library for pixel‑by‑pixel image comparison that runs in milliseconds, supporting common formats (PNG, JPEG, WebP, TIFF) and features such as anti‑aliasing detection, ignore regions, and diff image generation. It is provided as a fast command‑line tool and as Node.js bindings (including a persistent server mode), making it ideal for developers and CI pipelines that need high‑performance visual regression testing.