Project file created by BYOB (Build Your Own Blocks), a visual programming environment that is an extension of MIT's Scratch software; contains an arrangement of visual blocks and flows between the blocks that make up the data and logic for the program; enables saving and loading of programs.

While Scratch projects (.SB files) are used by younger audiences, BYOB projects were designed for use by computer science college students who do not declare computer science as their major. NOTE: BYOB is now developed under the name Snap!