Customer engagement platforms facilitate coordinated, personalized user interactions across multiple channels, such as email, SMS, and in-app messaging, to enhance product adoption, re-engage inactive users, and promote new offerings. They are particularly beneficial for large or rapidly expanding user bases, with the potential to transform fragmented campaigns into seamless, data-driven customer journeys that boost retention and growth. The guide reviews the top nine customer engagement platforms in 2025, highlighting their features, strengths, and ideal use cases. It emphasizes the importance of data flexibility, cross-channel coordination, scalability, and team enablement in selecting the right platform. Knock, Braze, Customer.io, Iterable, HubSpot, MoEngage, Klaviyo, CleverTap, and ActiveCampaign are evaluated for their capabilities, with Knock noted for its developer-friendly approach and robust notification infrastructure. The guide stresses the necessity of understanding message impact on user behavior to optimize engagement strategies, advocating for platforms like Knock that offer comprehensive tracking and iteration capabilities.