"The point that I’m trying to make here is that..."

Ever increasing invasive monitoring is still a crappy business decision.

Much like weaponizing Windows Update to the detriment of security and practices established by Microsoft...

Opt-Out is a crap and Microsoft should feel ashamed. Then again... they didn't feel ashamed when they made Windows Me and the stupid Start Replacement in 10...

It's a shame so many good steps (IE: Open Source) are marred by crap like Telemetry.

Persistent but not current session:
setx DOTNET_CLI_TELEMETRY_OPTOUT 1
Current session but non-persistent:
set DOTNET_CLI_TELEMETRY_OPTOUT=1

Thank you. I managed to apply the setx command a few times, but 39 out of 40 attempts it will throw "ERROR: invalid syntax - Type "SETX /?" for usage.

Those few times it worked I entered the exact same command you posted above. Not sure why this is happening. As mentioned, the set command works but it's temporary and ultimately useless.

I've just realised, the DOTNET_CLI_TELEMETRY_OPTOUT variable is removed from my computer every time I compile an application.
Microsoft becomes totally insolent and just ignores user settings.
Now I suspect, they're sending those data whether we want to do this or not!

Thanks for the instructions! But by proceeding the way you explained for Windows, I suspect that the environment variable is scoped to the current command line session, i.e. I will be opted-in again for example after the next reboot?

Many thanks for this, Mike!

Windows telemetry sometimes will consume 50% of my machine for long periods of time while I am trying to use my machine. Unless Microsoft is trying to copy my hard drive twice a day, there is no excuse for this. And if they are, then that is still no excuse. Until I am convinced that Microsoft fixes their telemetry gathering, I will always turn it off., disable it, corrupt the EXE, block that URL and whatever it takes so my machine sets me as the priority and does what I want first.