Cities have the capability of providing something for everybody, only because, and only when, they are created by everybody. Borrowing ideas from cyber world, the concept of open-source urbanism brings both formality and informality. Formal in its simple structure, the modular system with embedded infrastructure sets the basic unit and parameter for urban growth; informal in its open-source nature, this system could transform urban spaces by using modular building components to form larger societal hub and multiple city layers. Even though each separate module is simple, they form a new, highly rational urban system well-suited to the complexities of modern individuals and societies when they are grouped in a high-density algorithmic pattern. The module design possesses amazing customizability and is able to adapt to multiple urban environments, geographic cultures, individual lifestyles, and technological advancements. Its adoption will possibly influence future trends in architectural and urban design.