I am talking about the services which let you monitor the status of a website whether the website is up and operational or down or under heavy load.
how do they work under the hood?
for example:
I am building something similar for monitoring my web projects.
The answer that the status service websites will tell you: we automatically detect outages by performing http requests and checking responses for errors
the actual answer: some overworked developer gets woken up at 3am via pagerduty and manually set the status website to an outage state