rel="alternate" attribute value specifies that the linked page is an alternative version of the current page. The alternative can be in terms of device type, language, country, etc.
rel="alternate" on an <a> tag.
This link is to a Microsoft page for US users.
Go to <a rel="alternate" href="https://www.microsoft.com/en-us" target="_blank">Microsoft US</a>
The rel attribute defines the relationship between the current page and the linked page or resource.
rel="alternate" value tells search engines the linked page is an alternate to the current page.
This can be another page version in terms of device type, language, country, and more.
<tagname rel="alternate" />
These elements accept the alternate value on the rel attribute.
|<a>||Specifies an anchor link -- see example above|
|<area>||Creates clickable areas inside an image map.|
|<a>||Specifies an anchor link|
Here is when rel support started for each browser: