Courier

Novu is an open-source communication infrastructure platform that helps products and AI agents reach users across every major channel. It supports in-app notifications, email, SMS, push, chat, Slack, Microsoft Teams, Telegram, and custom channels from one unified system. Developers can add a notification inbox to an application with a lightweight component and scale into full workflow orchestration when needed. Novu includes user preferences, snooze, real-time delivery, digesting, workflow automation, and a block-based email editor powered by React Email. Its Novu Connect product helps AI agents communicate with users across channels such as Slack, email, Discord, and more. With open-source tooling, integrations, and a free plan, Novu helps teams build flexible notification and agent communication systems without starting from scratch.

The most powerful notification system you'll never build. Knock is flexible, reliable notifications infrastructure that's built to scale with you. Use our APIs to engage users, power cross-channel workflows, and manage notification preferences. Move fast with a notification engine that’s ready to scale from your first welcome email to a cross-channel system that puts your customer first. With Knock, you get a team that’s dedicated to one thing and one thing only: your notifications. Start with email and in-app channels. Instantly add push, SMS, and Slack when you need them. Predictable pricing that scales with you. No upfront fees or infrastructure set up required. Power high volume notifications without spending valuable engineering time on messaging infrastructure.