CommonStock is a developer of a group chat platform that is designed to share investment knowledge and decisions. It allows users to link any brokerage to shareholdings by percentage, get real-time alerts when friends buy/sell, copy each other's trades and invest together choosing their own amount, and compete to see who performs best, enabling users to coordinate trades as well as monitor and coach investment decisions. Commonstock’s product is currently available for free on the web and via an iPhone app (an Android-enabled app is forthcoming). The company was founded in 2017 by David McDonough and is headquartered in San Francisco, California.