Which codes are valid?

Google reads a two-letter ISO 639-1 language code, optionally followed by a script and a two-letter ISO 3166-1 country code, or x-default. en, en-GB and zh-Hant-TW are valid. en-UK is not (the code for the United Kingdom is GB), es-419 is not, and a country on its own, such as us, is not.

Why must a page list itself?

Google treats an hreflang set as one group that every member declares. A page that lists its alternates but not itself is missing from its own group.

Can it check the return links?

Not from one page. Every page in the set must link to all the others with the same tags, so paste each listed page in turn. A set with a missing return link is ignored for that pair.

Does it read hreflang in sitemaps or HTTP headers?

It reads and tags, so pasting the entry from a sitemap works too. Hreflang sent in an HTTP Link header has to be checked in the response headers.

Free tools · no sign-up

Hreflang checker

Paste a page's HTML and see whether its hreflang tags are ones Google will use, and which line is wrong when they are not.

The page's HTML, or just its head

This page's URL

Checked in your browser as you type. Nothing you paste is sent to domscout. To get the HTML, open the page, press Ctrl+U (Cmd+Option+U on a Mac) and copy everything.

Error (line 3) - "uk" is not a country code here. The United Kingdom is "GB", as in en-GB.

Error (line 4) - The href must be an absolute http or https URL.

Note - Every page in this set must link back to all the others with the same tags. Run each listed URL through this check to confirm the return links.

hreflang	URL	Line
en	https://example.com/en/	2
en-UK	https://example.com/uk/	3
de	/de/	4
x-default	https://example.com/	5

What Google needs from an hreflang set

Every URL is absolute, every value is a valid language or language and country, and each value names one URL.

Every page in the set lists itself and all the others, and each one links back. Google drops a pair when one side is missing.

The tags sit on the canonical version of each page. On a page whose canonical points elsewhere, Google follows the canonical and ignores the hreflang. To check these tags on every deploy instead of by hand, see automated hreflang checks.

Questions

No. You paste the HTML and the check runs in your browser as you type, so it also works on a page that is not live yet. Nothing you paste is sent to domscout.

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