It has a preview area that updates when you save your character. It can support fixed-width and variable-width fonts. And when you're done you can export the font in a few different formats.
It comes with a bunch of example fonts built-in. Also it's fully client-side code so you can save the webpage to use it offline.
If you want some inspiration for fonts, I made a bunch of really small fonts a few years ago: https://www.moonbench.xyz/projects/tiny-pixel-art-fonts/
