Ntfy

Ntfy is an open-source, HTTP-based pub-sub service that sends push notifications to your phone or desktop via simple PUT or POST requests.

Ntfy simplifies remote alerting by turning any curl command or HTTP request into a real-time push notification. You can trigger alerts from shell scripts, CI/CD pipelines, or IoT sensors without managing complex SDKs or registration flows. The service supports attachments, action buttons, and priority levels (1 to 5) to help you distinguish between a routine backup and a critical server failure. Because it is 100% open-source, you can use the public ntfy.sh instance for instant setup or self-host your own server to maintain total data sovereignty.

https://ntfy.sh