Managed detection and response (MDR) services emerged as an innovative entry in the security services landscape less than a decade ago. In 2021, the MDR market includes startups, endpoint vendors, managed security services providers (MSSPs), IT managed service providers (MSPs), consulting firms, outsourcers, and more. In the past year, we published “Now Tech: Managed Detection And Response Services Providers, Q4 2020,” followed by “The Forrester Wave™: Managed Detection And Response, Q1 2021.” This report synthesizes the data we collected from participating vendors and their customer references about their respective MDR service providers.