What is the default font?

What is the default font for HA? Or perhaps, what are the default fonts for HA? If I wanted to duplicate all font related aspects of HA’s default themes, I need to know that.

It is standard to comma separate fonts and include several in case the font is not found, like so:

      primary-font-family: "Times New Roman,Century"

Now I’m not actually using TNR or Century. I would like to do “MyCustomFont,HADefaultFont”. How can I achieve this?

Assuming you’re using Chrome, you can open “More Tools > Developer Tools” and with the Elements tab open, click on image and then click on an element on the page. If you then show the Computed style you can see the font in use.