Monday, April 08, 2013
in your webpage is a strong hint to search engines your about preferred version to index among
duplicate pages on the web.
It's supported by several search engines, including
and Google. The
rel=canonical link consolidates indexing properties from the
duplicates, like their inbound links, as well as specifies which URL you'd like displayed in
search results. However,
rel=canonical can be a bit tricky because it's not very
obvious when there's a misconfiguration.
While the webmaster sees the "red velvet" page on the left in their browser, search engines notice
on the webmaster's unintended "blue velvet"
rel=canonical on the right. We recommend
the following best practices for using
- A large portion of the duplicate page's content should be present on the canonical version.
Double-check that your
rel=canonicaltarget exists (it's not an error or "
rel=canonicaltarget doesn't contain a noindex robots
Make sure you'd prefer the
rel=canonicalURL to be displayed in search results (rather than the duplicate URL).
rel=canonicallink in either the
<head>of the page or the HTTP header.
Specify no more than one
rel=canonicalfor a page. When more than one is specified, all
rel=canonicallinks will be ignored.
rel=canonical to the first page of a paginated series
Imagine that you have an article that spans several pages:
- and so on
rel=canonical from page 2 (or any later page) to page 1 is not correct
rel=canonical, as these are not duplicate pages. Using
rel=canonical in this instance would result in the content on pages 2 and beyond not
being indexed at all.
Mistake 2: Absolute URLs mistakenly written as relative URLs
<link> tag, like many HTML tags, accepts both relative and absolute URLs.
Relative URLs include a path "relative" to the current page. For example,
images/cupcake.png means "from the current directory go to the
subdirectory, then to
cupcake.png." Absolute URLs specify the full path—including the
<link rel=canonical href="example.com/cupcake.html" /> (a relative
URL since there's no
https://) implies that the desired canonical URL is
https://example.com/example.com/cupcake.html even though that is
almost certainly not what was intended. In these cases, our algorithms may ignore the specified
rel=canonical. Ultimately this means that whatever you had hoped to accomplish with
rel=canonical will not come to fruition.
Mistake 3: Unintended or multiple declarations of
Occasionally, we see
rel=canonical designations that we believe are unintentional. In
very rare circumstances we see simple typos, but more commonly a busy site owner copies a page
template without thinking to change the target of the
rel=canonical. Now the site
owner's pages specify a
rel=canonical to the template author's site.
If you use a template, check that you didn't also copy the