"fast.com" is being queried every 15 seconds - how do I find out what's doing it?

on my laptop, I’m seeing fast.com being hit every 15-20 seconds…

fully 25% of my DNS traffic is hitting that domain.

On OSX, how do I find out what’s asking for this?

Thanks!

I would use WireShark. https://www.wireshark.org/download/osx/ and there is an option to turn on DNS resolution when you start a capture I would use that as well.

Another option.
I have released My Pi-hole log extractor tool written in QB64 https://github.com/smokingwheels/smokingwheels.github.io/blob/master/qb64/piholelogext.bas . You may need help to run it on OSX Feel free to post my program on the http://www.qb64.net/ Forum, ask for help as I don’t have any OSX PC’s.
If you find it useful I would like to add it to my Github site for others to use.