I did a bunch of work with extracting info from fonts for a site I built last year [1], a useful tool to know about if you want to do something like this yourself (e.g. automating extraction of data from fonts) is ttx [2] from the fonttools package (available for Python and also a CLI tool which can be brew installed), which can dump out all of the tables in the font (which is where all the information about the glyphs and variations etc. is stored) to XML. There’s a lot of data (fonts are amazingly complex things with all the OpenType features, variable support [3] etc) and the structure takes some working out, but it’s all in there!

There’s also opentype.js [4] which can do similar on the client side, I’m not sure if there’s some info that you can only get from ttx or if opentype.js exposes all the same information off the top of my head.

Finally, Fontforge [5] is an OSS font editor which can be useful for inspecting the glyphs in a font visually etc.

[1] https://f37foundry.com

[2] https://fonttools.readthedocs.io/en/latest/ttx.html

[3] https://f37foundry.com/playground has some fun examples of what you can do creatively with variable fonts (best on desktop)

[4] https://github.com/opentypejs/opentype.js

[5] https://fontforge.org/en-US/