x-default is a special value used in hreflang annotations. It tells search engines which URL to show users whose language or location matches none of the alternate versions you have declared. It is commonly pointed at a language selector page or at the site's main, usually English, version.
How to use it
Add x-default alongside your other hreflang entries, in the same set that appears on every alternate page. It can go in HTML link elements, in HTTP headers for non-HTML files, or in the XML sitemap. Only one x-default should exist per set.
<link rel="alternate" hreflang="en" href="https://example.com/" />
<link rel="alternate" hreflang="de" href="https://example.com/de/" />
<link rel="alternate" hreflang="fr" href="https://example.com/fr/" />
<link rel="alternate" hreflang="x-default" href="https://example.com/" />What to point it at
If your site has a country or language picker, x-default often points there. If not, point it at the version most useful to the widest audience. It may share a URL with another entry, such as en, which is normal and allowed.
Rules that still apply
x-default follows the same rules as other hreflang values. The set must be reciprocal: each page lists all versions including itself. URLs must be absolute, indexable and canonical, and should return a 200. An x-default pointing to a redirect or a noindexed page weakens the whole set.
Example
A fallback for unsupported languages
Emberdock, a developer tooling SaaS, publishes English, German and Japanese versions of its docs. Visitors searching in Spanish were landing on the Japanese pages in some cases. Adding an x-default entry pointing at the English docs gives Google an explicit fallback for languages the site does not cover.
Common mistakes
Adding x-default on only one page
It must appear in the hreflang set on every alternate page, not just the homepage.
Pointing it at a geo-redirecting URL
If the x-default URL redirects users by IP, crawlers may never see a stable page. Use a page that returns 200 for everyone.
Questions
No, but Google recommends it. Without it, Google picks a fallback itself for users who match none of your versions.
