Opening DevTools and scrolling through hundreds of computed properties works, but it is slow when all you wanted was the name of a typeface.
Esc or click the icon again to turn it off. The page is left exactly as it was.The panel reports what the browser actually applied, not the text of the original stylesheet. So a line height may read 27.2px rather than the 1.7 someone wrote, and a font family appears as the resolved stack. When a font file comes from a stylesheet hosted on another site, the panel says so instead of guessing.
Pro exports every color and font on the page as CSS variables or JSON, and can list the page's images, background images and font files. It is $2.99 / month or $24 once, and the free inspection above has no limit and needs no account.
Nothing leaves your browser: there is no server, no account, no analytics. The extension reads only the tab where you clicked the icon. It cannot run on chrome:// pages, the Chrome Web Store or the built-in PDF viewer — the icon shows "!" there.