Thunderclap is an online platform that allows users to coordinate social media posts across multiple networks to amplify messages. It works by having supporters pledge to share a single message on their social media profiles on a specific date, functioning like an "online flash mob". To use Thunderclap, users create an account, start a campaign by providing a message, deadline, and support goal. On the deadline, the message will be simultaneously posted on all supporters' networks, amplifying its reach. Thunderclap can help promote causes, products, or events through coordinated online word-of-mouth sharing.