Notification Infrastructure APIs let you add notification infrastructure capabilities without building from scratch. Every entry below is profiled with trust signals — pricing model, authentication requirements, CORS support, rate limits, and live uptime checks — so you can compare options and pick production-safe choices instead of guessing from a link list.
| API | Pricing | Auth | CORS | Health | |
|---|---|---|---|---|---|
| Courier API Courier API for multi-channel notifications: design, build, and send notifications via email, SMS, push, and chat with unified API. | Freemium | API Key | No | Profile | |
| Knock API Knock API for transactional product messaging: multi-channel delivery across email, push, SMS, and in-app with workflow orchestration. | Freemium | API Key | No | Profile | |
| Novu API Open-source notification infrastructure API for workflows, subscribers, topics, and integrations. | Freemium | API Key | Yes | Profile |
Start with pricing and auth: free tiers and no-auth APIs are fastest to prototype with. Then check CORS if your app calls the API from the browser, and health before you commit — a great API that's been down for a week will block your launch. Each profile below shows all of these signals plus rate limits where documented.