Browser extension
Page Font Inspector
Inventory every font family, weight, style and size a page renders, plus its @font-face sources.
A typography audit in one click: a deduplicated inventory of every font stack the page actually uses, the @font-face rules behind them, and a click-to-inspect mode for a single element.
Privacy: runs entirely in your browser, on the active tab, only when you click. No account, no network requests, no data collected.
Get it for Firefox Not on the Chrome Web Store yet
The Firefox version is live on addons.mozilla.org. A Chrome Web Store listing is planned but not published; this page will link it when it exists.