x-default

x-default is a reserved value of the hreflang attribute. Where every other hreflang value names a language, or a language and a region, x-default names no language at all: it marks the version of a page to offer someone whose language settings match none of the versions you list.

What Google says it is for#

Google's documentation on localized versions describes x-default as the value "used when no other language/region matches the user's browser setting". It recommends the value for that fallback page and adds that x-default was designed for language selector pages, so it works best when it points at one. Google's page describes it as recommended.

x-default follows the same rule as every other entry: each version of the page lists itself and all the others, so the x-default line belongs in the set on every version, pointing at the same address everywhere.

Two ways to use it#

A site whose homepage is a chooser, a page that asks the visitor to pick a country or language, points x-default at that chooser. This invented example has a chooser at /choose/ and two language versions:

<link rel="alternate" hreflang="en" href="https://example.com/en/" />
<link rel="alternate" hreflang="tr" href="https://example.com/tr/" />
<link rel="alternate" hreflang="x-default" href="https://example.com/choose/" />

A reader in Japan, whose browser asks for Japanese, matches neither en nor tr and is offered the chooser.

Most sites have no chooser. They write their pages in one language and translate them, and for them the natural fallback is the original: a visitor nobody wrote a version for gets the language the site was built in. Then x-default and one of the language entries point at the same URL.

What x-default should not point at is a URL that sends each visitor somewhere different, for instance by reading the browser's language. Googlebot sends no language preference with its requests, as the Accept-Language header entry explains, so it would only ever see one of the destinations.

x-default in LangRelay#

LangRelay's WordPress plugin writes the hreflang set on every page that has an activated translation and on its original, and its x-default entry points at the original page, the version in your Source locale. You do not maintain the entry by hand: the set is built from the same list of live translations for every version, so it stays the same on all of them.

The article on self-referencing hreflang and x-default answers the two questions this entry raises with full markup, including how five WordPress plugins set x-default. The hreflang guide covers the rest of the attribute.