Saniten Tan, often referred to as 3.1-tan, is a personification of Microsoft Windows 3.1 in the OS-tan meme series. Cute, retro, and slightly old-fashioned, she typically appears in clothing reminiscent of early 90s office fashion. Saniten is portrayed as knowledgeable but sometimes struggles with modern technology. In the OS-tan universe, she represents the stability and simplicity of early graphical operating systems, acting as a reliable and nostalgic figure among the other OS-tan characters.