<small> represents side comments or small print, such as copyright or a brief qualification. It has meaning independent of font size; it is not a wrapper for every piece of less important content.
A concise qualification
The qualification stays visible and readable. Its smaller type is ordinary presentation.
HTML and CSS
HTML
<p>Workshop admission: $20.</p>
<p><small>Materials are included. Travel is not included.</small></p>CSS
small {
font-size: 0.9rem;
}Edit HTML or CSS to update the preview as you type. Copy code snippet copies the selected tab. Preview spacing and font defaults are not included.
Content and appearance
Small accepts phrasing content and global attributes. It can appear inside a paragraph or alongside other text. Use normal paragraphs for a long disclaimer or full terms document instead of shrinking the whole thing.
Do not use small to hide critical information or reduce important instructions until they are hard to read. A qualification may be legally or practically significant even though it is marked as a side comment.
Alternatives and exercise
Set small { font-size: 1rem; }: the side-comment meaning remains. Use font-size when all you need is a size change. Use sup for a typographical footnote marker, with a real link to the note; sup does not itself supply the note’s content.
Sources and browser support
MDN: small describes the syntax and links to the specification and compatibility data. Check individual values in that table when supporting older browsers.