The <aside> tag

<aside> marks content tangentially related to the main content — a sidebar, related links, callout boxes.

Syntax

<aside>...</aside>

Example

<aside>
  <h3>Related posts</h3>
  <ul><li><a href="/post-2">Another post</a></li></ul>
</aside>

Notes

aside inside an article relates to that specific article (e.g. a footnote); aside at the page level is a general sidebar.

Accessibility

aside has an implicit ARIA role of complementary.

Related tools

The <main> tag

Purpose of <main>: the page's unique primary content, excluding repeated elements.

The <section> tag

Purpose of <section>: grouping thematically related content, usually with its own heading.