The most common semantic HTML question answered with a decision flowchart. Answer each question to find out which element fits your content.
These are the semantic mistakes hiding in nearly every codebase. Click a tab to see the wrong usage, the correct usage, and why it matters.
font-size. If you're marking up legal fine print, <small> is the right element.Build a heading structure by clicking the buttons. The outline updates in real time. Invalid heading jumps (e.g. h1 → h3) are flagged in red. One h1 per page — the document outline algorithm was never implemented by browsers.
HTML5 introduced a sectioning algorithm allowing multiple <h1> elements. No browser or screen reader ever implemented it. The W3C confirmed this in 2013 and again in 2019. Always use one <h1> and nest h2–h6 below it.
Click any element to see what it does, when to use it, and a working code example.
Real-world HTML templates showing correct semantic structure for the three most common page types. Copy and adapt for your projects.