Will +1’s from my site show up in search results?

If a user +1’s a URL on your site, the Google search result snippet for that URL may be annotated in search results and search ads.

However, your site may make the same content available via different URLs. For example, your site may have several pages listing the same set of products. One page might display products sorted in alphabetical order, while other pages display the same products listed by price or by rating. For example:

http://www.example.com/product.php?item=swedish-fish&sort=alpha
http://www.example.com/product.php?item=swedish-fish&sort=price

If Google knows that these pages have the same content, we may index only one version for our search results. As a result, +1's for the other versions may not appear in search results.

You can make sure Google displays +1 annotations for the most search results possible by adding the rel="canonical" property to the non-preferred versions of each page. This property should point to the canonical version, like this:

<link rel="canonical" href="http://www.example.com/product.php?item=swedish-fish&sort=alpha">

This tells Google: "Of all these pages with identical content, this page is the most useful. Please prioritize it in search results."

Now, when a user +1’s a page with a non-canonical URL, Google will associate that +1 with the canonical, preferred version.