A marketing manager wants to understand which of their recent campaigns are most effective at bringing new users to their website for the very first time. They need to identify the original marketing channels for these first-time visitors. Which standard report in Google Analytics is specifically designed to answer this question?

They should use the User Acquisition report. It is built on first user dimensions, so it attributes each user to the channel that brought them to the site for the very first time and keeps that attribution regardless of how they return later. That is exactly what the manager is asking: which campaigns recruit genuinely new people. The natural comparison is the Traffic Acquisition report, which is session-scoped and shows which channels bring visits, including repeat visits from people acquired elsewhere. Both are useful and they answer different questions. Channels like email, direct and brand search tend to look strong on traffic acquisition because they bring existing customers back, while discovery channels such as paid social, display and generic search usually show their value in user acquisition.