BCI2000 is a general-purpose open-source software platform for brain-computer interface research, developed since 2000 at the Wadsworth Center of the New York State Department of Health with contributions from the University of Tübingen and many labs worldwide. BCI2000 can incorporate any brain signals, signal processing methods, output devices, and operating protocols in a modular architecture. The platform is free for research and education, used in 110+ laboratories worldwide with 11,000+ users and 2,500+ peer-reviewed publications. BCI2000 was used in the first experiment to transmit brain signals over the internet.