What are the specific fonts used in Streamlit's UI?

I need to look up whether some glyphs are available.

I’d also like to know this

The fonts used are a function of what your browser has installed, but you can quickly see what is being displayed using the browser developer tools:

In my case with Chrome on Ubuntu, the font-family is “Source Sans Pro”, but on more mainstream operating systems (Windows, Mac) I suspect they will be different.