its <a>content language</a>, as represented in BCP 47 syntax,

matches the given <a>language range</a> in an <i>extended filtering</i>

operation per [[!RFC4647]] <cite>Matching of Language Tags</cite> (section 3.3.2).

Both the [=content language=] and the [=language range=]

The [=content language=] and the [=language range=]

must be <i>canonicalized</i>

and converted to <i>extlang form</i> as per section 4.5 of [[!RFC5646]]

prior to the <i>extended filtering</i> operation.

prior to the <i>extended filtering</i> operation;

language tags or ranges that are not

<a href="https://www.w3.org/TR/i18n-glossary/#dfn-valid">valid</a>

do not match anything.

The matching is performed [=ASCII case-insensitively=].

The <a>language range</a>

(<a href="https://github.com/w3c/csswg-drafts/issues/8720">Issue 8720</a>)

* Reworded constraints on language ranges

(<a href="https://github.com/w3c/csswg-drafts/issues/8720">Issue 8720</a>)

<!-- to 27 May 2026 -->

* Clarified that :picture-in-picture applies to the embedder element, not the PiP display

(<a href="https://github.com/w3c/csswg-drafts/issues/13720">Issue 13720</a>)

* Renamed &lt;an+b> to &lt;a-n-plus-b>

(<a href="https://github.com/w3c/csswg-drafts/issues/9473">Issue 9473</a>)

* Added CanIUse panels

(<a href="https://github.com/w3c/csswg-drafts/issues/1193">Issue 1193</a>)

* Forbade non-valid tags/ranges from ever matching

(<a href="https://github.com/w3c/csswg-drafts/issues/3022#issuecomment-4568519381">Issue 3022</a>)

<!-- to 2 July 2026 -->

<h3 id="changes-2022-11">

Changes since the 11 November 2022 Working Draft</h3>