demo · v140

H1 Font-size Rule

Pre-v140 the UA stylesheet shrunk nested <h1>s inside <article>, <section>, <aside>. Toggle to see the old vs new rendering — and a live probe of your browser's actual computed size.

simulated rendering

Top-level H1

article >

H1 inside article

section >

H1 inside section

your browser, real measurements

measuring…
/* Pre-v140 UA stylesheet (deprecated): */
article h1, section h1, aside h1 { font-size: 1.5em; }
/* v140+: removed. All <h1>s render at the standard 2em
   unless your stylesheet says otherwise. */

see also