**`<h3>`** headings break an `<h2>` section down further into subsections. Continuing the document-outline analogy, if `<h1>` is the book title and `<h2>` are chapters, `<h3>` are the subsections within each chapter. This nesting should follow the numeric order strictly — an `<h3>` should always be logically 'inside' the most recent `<h2>`, not appear as a standalone top-level section.
1Understanding <h3>
`<h3>` headings break an <h2> section down further into subsections. Continuing the document-outline analogy, if <h1> is the book title and <h2> are chapters, <h3> are the subsections within each chapter. This nesting should follow the numeric order strictly — an <h3> should always be logically 'inside' the most recent <h2>, not appear as a standalone top-level section.
A quick way to audit heading structure: list every heading on the page in order — it should read like a coherent, properly nested table of contents, with no level jumps.
<h2>Setting Up Your Environment</h2>
<h3>Installing Node.js</h3>
<p>...</p>
<h3>Installing a Code Editor</h3>
<p>...</p>2Practical Example
Here is a real-world application of <h3> showing how it is used in production HTML.
<!-- Deeper documentation structure -->
<h1>API Reference</h1>
<h2>Authentication</h2>
<h3>API Keys</h3>
<h3>OAuth Tokens</h3>3Best Practices
Follow these guidelines when working with <h3>:
1. Use <h3> only for subsections within a preceding <h2>, not as a top-level section on its own
2. Keep the nesting logical: don't place an <h3> before any <h2> has appeared
3. Style with CSS if you need a different visual size — don't pick a heading level purely for appearance
Tip: A quick way to audit heading structure: list every heading on the page in order — it should read like a coherent, properly nested table of contents, with no level jumps.
<h2>Setting Up Your Environment</h2>
<h3>Installing Node.js</h3>
<p>...</p>
<h3>Installing a Code Editor</h3>
<p>...</p>