The best broker for a demat account depends on the individual investor's needs and preferences. Some of the most popular brokers for demat accounts include Zerodha, Upstox, 5Paisa, Angel Broking, ICICI Direct, HDFC Securities, Motilal Oswal, and Sharekhan. Each of these brokers offers different features and services that may be beneficial to different types of investors. It is important to research each broker to find the one that best suits your needs.