For questions primarily about D&D Beyond, the official Dungeons & Dragons 5th Edition digital service (including sourcebooks and related tools) developed by Fandom Games (formerly known as Curse) for Wizards of the Coast.
D&D Beyond (officially abbreviated as DDB) is a service launched in 2017. It was developed by Fandom Games (formerly known as Curse), and is officially sanctioned by Wizards of the Coast to host official Dungeons & Dragons 5th Edition content. It includes D&D 5e sourcebooks and related tools.
D&D Beyond has both a website and mobile apps on Android and iOS.