If the JavaScript is small and efficient, I would guess the overhead is little more than the extra roundtrip that you'd avoid if you just delivered the HTML pre

If the JavaScript is small and efficient, I would guess the overhead is little more than the extra roundtrip that you'd avoid if you just delivered the HTML pre-baked. A slight aside: Dynamically producing HTML (avoiding client-side JavaScript) is now back in vogue with a rather silly buzzword: server-side rendering. Presumably coined by someone who doesn't understand what 'render' means. https://alligator.io/react/server-side-rendering/ https://alligator.io/react/server-side-rendering/