https://stats.uptimerobot.com/81NqJuOD8 Monitor sites’ uptime. We have up to 50 monitors for the free plan but I think it is lower now. Sends notifications when a site goes down. You can set it to check https, ping or http every 24 hours down to 5 mins (free plan).
This was being used to monitor uptime for the VPSs. It can monitor sites too. Uptime Robot allows us 50. Using this sometimes for VPS monitoring. Here is our page.
Hopefully this can replace the others. Now has its own page.
This is freshworks service. It gives 50 monitors on the free plan, up to 1 mins interval. Not used yet but may be good to have later.
Up to 5 hosts on free plan. This may not be much use for domain monitoring but for monitoring the hosts perhaps. More info should be got! https://www.datadoghq.com/pricing/
10 free checks in the free plan. https://betteruptime.com/pricing
15 uptime and 32 blacklist montors for free. https://hetrixtools.com/
Maybe we can use this when we have too many accounts to monitor for free.
see also Speed Test VPS