Well, this is pretty confusing mainly because the Chrome developer tools keep changing, but for November 2019, here is how to do it:
- Download Chrome
- Enable Developer tools
- Start them with View/Developer/Developer Tools
- Now a window opens on the left, you want to click on the upper left icon there called
Select Item to Inspect Itwhich is also Command-Shift-C on a Mac, then the right screen should change
- Highlight any element and in a popup box, you will see the Font type. For instance, the default in WordPress right now is Noto Sans.