Dynamic sites often produce syntactically different URLs for the same page. Multiple variant URLs can lower the search engine ranking of a page. Canonicalizing URLs reduces the duplicate content and improves search engine ranking.
Many search engines base their relevancy ranking algorithms on the number and quality of links that point to a particular page. The more links there are that point to a particular page, the higher the page rank. Multiple URLs generated by a dynamic site can lower the ranking of a page because, to the search engine, each version of the URL appears to point to a different page.
For example, users might be able to reach a Napa Red wine page by first clicking on “Napa” and then clicking on “Red”, or by first clicking on “Red” and then “Napa.” This creates two syntactically unique links pointing to the same Napa Red page:
To the search engine, each version of the URL appears to be its own unique page with identical or near-identical content, and each page takes a portion of the link references.
To improve quality, search engines try to minimize the appearance of largely similar pages within results sets. Among other strategies, all indexed pages are evaluated for duplicates and near-duplicates before a page is selected to be displayed in the search results. In the case of the Napa Red page, only one of the two URLs would be selected -- and therefore only half of the link references are evaluated. This link dilution of the Napa Red page may result in a lower position within search results. Multiple parameters in URLs have the same effect.
In order to avoid multiple versions of URLs per page, links throughout the site should be standardized (canonicalized), and requests for a non-standard version of the URL should be redirected to the canonical version via a "301" (permanent) redirect.
By design, the URL optimization classes prevent the creation of
syntactically different URLs by canonicalizing keywords, ensuring that
equivalent pages have URLs with the same syntax even if they can be navigated
to through different paths. You can choose from a number of configuration
options to control the arrangement of keywords. For example, you can configure
your
UrlFormatter object to arrange dimensions alphabetically
in an ascending order:
Now even if a user navigates to "Red" before "Napa", the link still
appears as
/Region-Napa/Wine-Red.
Related links
