Horos is a free and open-source medical imaging application tailored for macOS, providing a comprehensive 64-bit DICOM viewer that caters to the needs of the medical imaging community. Developed from OsiriX 5.8, it serves purposes in research, education, and non-diagnostic medical imaging contexts. This versatile tool can handle a broad spectrum of DICOM files and boasts advanced features like 2D/3D multi-planar reconstruction, surface and volume rendering, and maximum intensity projection. Users can seamlessly view, import, and export studies, measure anatomical structures, annotate images, and utilize filters or adjustments for enhanced visualization. Furthermore, Horos includes anonymization capabilities, DICOM Query/Retrieve functions from PACS servers, and supports plugins and scripting, allowing for extensive customization. The user interface is both intuitive and flexible, making it suitable for beginners and seasoned professionals alike, and it integrates well with educational materials and teaching workflows. Additionally, its ongoing updates and community support ensure that Horos remains relevant and effective for various medical imaging needs.