Google-AMP > HEAD and Sitemap

Question

I've read about AMP and I've got a question.

Usually our HEAD (for non-AMP sites) looks like

<link rel="canonical" href="https://www.example.com/de/Some-Page-German">
...
<link rel="alternate" hreflang="de" href="https://www.example.com/eu/Some-Page-German">
<link rel="alternate" hreflang="en" href="https://www.example.com/eu/Some-Page-English">
<link rel="alternate" hreflang="en-de" href="https://www.example.com/de/Some-Page-German">
<link rel="alternate" hreflang="de-de" href="https://www.example.com/de/Some-Page-English">

In Google Search Console we submit two sitemaps. One for /de and one for /eu those sitemaps contain only one URL of the product since Google should see the other versions anyway in the head.

Now my main question - if I now create a AMP Version of the page the head should be like (AMP version would be reachable under example.com//amp/Some-Page:

<link rel="canonical" href="https://www.example.com/de/Some-Page-German">
...
<link rel="alternate" hreflang="de" href="https://www.example.com/eu/amp/Some-Page-German">
<link rel="alternate" hreflang="en" href="https://www.example.com/eu/amp/Some-Page-English">
<link rel="alternate" hreflang="en-de" href="https://www.example.com/de/amp/Some-Page-German">
<link rel="alternate" hreflang="de-de" href="https://www.example.com/de/amp/Some-Page-English">

So the rel tags point to the other mapping AMP pages but the canonical Tag points to the non AMP version.

I assume that's correct so far.

But how do I tell Google (and other Search Engines) now that there is an AMP version?

Do I need to adjust my sitemaps to only include the AMP version of each page so Google checks and see's all AMP versions + normal version through canonical tag? If so wouldn't it lead to problems because of other search engines perhaps not "supporting" AMP that well therefore indexing the wrong page?

Or do I need to add another Tag to main non AMP version of page rel="alternate" to mention the AMP version?

Answer 1

Simply place another rel="amphtml" tag on your non AMP version pointing to the AMP version of the page.

<link rel="amphtml" href="https://www.example.com/url/to/amp-version.html" />

In your sitemaps keep the non AMP versions. Goolge will see the rel-Tag and crawl the AMP versions too.

On the AMP page no extra tag besides the canonical tag pointing to the non AMP version is required.

See https://support.google.com/webmasters/answer/6340290?hl=en