PS-MRTG
MRTG-style bandwidth monitor for Windows, one PowerShell script
...It is a single PowerShell script that reads each interface and plots incoming and outgoing throughput in a browser dashboard, live and over time (hour, day, week), in the spirit of the classic MRTG brought to the Windows world.
There is no agent, no service and no external dependency. Counters are read through Get-NetAdapterStatistics, usually without admin rights, so it runs on locked-down and offline machines as well as ordinary ones. It works with ConstrainedLanguage, Windows PowerShell 5.1 and PowerShell 7+, and adds a CSV export and a configurable alarm threshold.
Free and open source, MIT licensed. Code on GitHub, also on the PowerShell Gallery.