systemd is a replacement for the init daemon for Linux (either System V or BSD-style).
SaaSHub's Down Detector checks the status of services automatically and regularly. However, we cannot promise 100% accuracy. That is why we depend on user reported issues as well. The Supervisor status here can help you determine if there is a global outage and Supervisor is down for everyone or it is just you that is experiencing problems. Please always report any issues to help others know the current status.