glyphhanger

glyphhanger is a command-line tool that reads a web page or a local file and lists the characters its text uses as a Unicode range. With --subset, it writes smaller copies of font files that keep only those characters, in TTF, WOFF or WOFF2 format. With --css, it also writes a @font-face block for the subset files. It can follow local links with a spider, and limit the result to text in one font family or to visible text.

Worth knowing

Subsetting needs pyftsubset from fonttools, which needs Python. By default the page reader runs Puppeteer with headless Chrome; a --jsdom mode reads pages without it.