In-app messaging is a vital tool for engaging users within applications by delivering notifications that drive actions and provide information contextually. Understanding the diverse types of in-app messages, such as notification feeds, inboxes, cards, modals, banners, and toasts, is essential to developing an effective messaging strategy. Each message type serves different purposes depending on whether the notification is transactional or promotional and the level of user attention required. For instance, notification feeds are suitable for transactional messages that must be accessible, while modals are effective for capturing immediate attention. Best practices emphasize considering user activity, prioritizing user experience by avoiding message overload, and employing segmentation and personalization to enhance relevance. Cross-channel experiences can be optimized by integrating in-app messages with other channels, such as email, to deliver more personalized and timely content. Companies like Knock offer infrastructure to support diverse in-app messaging and cross-channel delivery, helping businesses create a more engaging and user-friendly experience.