`hreflang.absolute`

Default: error
Plugin: hreflang

An hreflang link uses an absolute URL.

Why: Search engines require absolute URLs in alternate links.

When off: relative alternate links pass.

<!-- ✗ Fails -->
<link rel="alternate" hreflang="en" href="/en/" />

<!-- ✓ Passes -->
<link rel="alternate" hreflang="en" href="https://example.com/en/" />

References

Google: Localized versions of your pages: Alternate URLs must be fully qualified.