Google introduced new SEO specific attributes for handling multi-lingual pages and content. The new attributes are rel=”alternate” and hreflang=”x”. It looks something like this when used in the source code of your files:
<link rel=”alternate” hreflang=”a-different-language” href=”http://url-of-the-different-language-page” />
Google says it should be used when (1) template (i.e. side navigation, footer) is machine-translated into various languages, and/or (2) main content remains unchanged, creating largely duplicate pages.
The attributes should be used in conjunction with the rel=”canonical” or 301 redirects you have set up. The Google post goes into detail on how it should be used, but in summary, there are two steps:
Step 1: Once you have the canonical picked out you can use either rel=”canonical” or a 301 (permanent redirect) from the various localized pages to the canonical URL.
Step 2: On the canonical URL, specify the language-specific duplicated content with different boilerplate via the rel=”alternate” link tag, using its hreflang attribute. This way, Google can show the correctly-localized variant of your URLs to our international users.