Macintosh.js is an open-source project that allows users to emulate classic Macintosh computers directly within a modern web browser. Developed using JavaScript, Macintosh.js recreates the experience of using older Macintosh systems, such as the Macintosh Plus, Macintosh SE, and Macintosh II. This emulation includes the iconic Macintosh graphical user interface (GUI), system software, and applications like MacPaint and MacWrite. The project aims to preserve and make accessible the historical software and user interface designs of early Macintosh computers. It leverages modern web technologies to provide a seamless emulation experience, enabling users to run old Macintosh software and explore computing history without the need for physical hardware. Macintosh.js is particularly valuable for retro computing enthusiasts, educators, and historians interested in studying or experiencing the evolution of personal computing interfaces. Its open-source nature encourages community contributions and improvements, ensuring continued compatibility and accuracy in emulating vintage Macintosh systems. Overall, Macintosh.js serves both as a tribute to Apple's early innovations and as a practical tool for studying the evolution of computing interfaces and software design.