Hreflang is the tag that tells Google "this page and that page are the same content, just in different languages or for different regions — show whichever one matches the visitor." It sounds simple and the syntax is genuinely small, but hreflang has a reputation as one of the most commonly misconfigured elements in SEO for a specific reason: a single missing return link anywhere in the set quietly breaks the whole thing, with no error message and no obvious symptom beyond "wrong version in wrong country."

The syntax

Hreflang tags live in the <head> of each page version, one <link> tag per alternate version, including a self-referencing tag pointing to the page itself:

<link rel="alternate" hreflang="en-gb" href="https://example.com/uk/" />
<link rel="alternate" hreflang="en-us" href="https://example.com/us/" />
<link rel="alternate" hreflang="fr" href="https://example.com/fr/" />
<link rel="alternate" hreflang="x-default" href="https://example.com/" />

The hreflang value is a language code, optionally followed by a region code: en for English generally, en-gb for English specifically in the UK, fr-ca for French in Canada. x-default is a special value marking which version to show visitors who don't match any of your specified language-region combinations — typically your main or most general page.

The rule almost everyone gets wrong: reciprocity

Every page in a hreflang set must link back to every other page in the set, including itself. If your UK page lists the US and French versions as alternates, the US and French pages must each list the UK version right back — and each other. Miss one return link anywhere in the chain and Google is explicit about what happens: it discards the entire hreflang cluster for that page, not just the broken link. This is why hreflang errors tend to appear in waves across a whole site rather than as isolated single-page issues — one systemic mistake (a template bug, a page added without updating its siblings) breaks reciprocity everywhere at once.

Common mistakes beyond missing return links

  • ◆Wrong language or region codes. Codes follow ISO 639-1 (language) and ISO 3166-1 Alpha 2 (region) — en-gb is correct, en-uk is not a valid region code and will be silently ignored.
  • ◆No self-referencing tag. Each page needs to list itself as one of its own alternates. Skipping this is a common template oversight that weakens the whole set.
  • ◆Conflicting signals. If your hreflang says a page is en-us but the page's own canonical tag points somewhere else entirely, or the content is duplicated word-for-word with no actual localization, Google treats the hreflang set as unreliable.
  • ◆No x-default. Without it, visitors who don't match any specific language-region combination get Google's best guess instead of the fallback you'd choose — usually not what you want for, say, a visitor from a country you don't have a dedicated version for.
  • ◆Assuming hreflang replaces proper localization. Hreflang routes visitors to the right version; it doesn't make machine-translated or thin content rank. The underlying pages still need to be genuinely useful in each language.

Tip If you manage more than two or three language versions, declare hreflang in your XML sitemap rather than in-page <link> tags — it's centralized in one file instead of scattered across every page template, which makes auditing and fixing reciprocity errors considerably easier as the set grows.

Checking your current setup

Because the failure mode is invisible (no error on the page itself, just Google quietly defaulting to its own judgment), hreflang is one of those technical SEO elements worth actively checking rather than assuming is fine. Our free hreflang checker reads a page's hreflang tags, validates the language-region codes, and — critically — fetches each alternate page to confirm it actually links back, catching exactly the reciprocity failures that are otherwise invisible until a visitor reports seeing the wrong country version.

International SEO touches a lot of the same technical foundation as XML sitemaps and canonical and indexing signals — worth reviewing both if you're expanding into new markets. If you're planning a genuine multi-region launch, our digital marketing services cover the full technical and content localization setup, not just the tags.