I wonder how that's calculated. The traditional measure is ^VIX, which not very high at all right now.

I am so glad you asked that.

The fear greed index appears to be the same value as the CNN one. The CNN one has a link to explain it. https://www.cnn.com/markets/fear-and-greed

Being the pessimist I am I wonder when and how they change their criteria.

That's the scary part