Internet-Check allows you to check internet connectivity periodically by pinging preset servers, and it logs any time offline.
This little Open Source tool will be useful to find connectivity issues that occur, allowing you to determine if there is a pattern to the times your machine is offline. This can be essential if you allow automatic Windows updates, for instance, set to happen during downtimes like overnight, and they keep failing.
Internet-Check works by pinging Google's DNS and Cloudflare at user-defined intervals and logging any time within the range spent offline. The author notes that you should opt to ping at intervals greater than 30 seconds, or the potential for this action to be considered a DDoS attack exists.
Internet-Check is displayed from a simple UI that does include a few options like dark mode, start with windows, and show only in systray when minimized. There are no other options available, and the selected servers are the only choice.