Learn about Canonical tags and Possible Misuse
WRITTEN by: Jerrod Swanton |
categories:
SEO
When moving a website to a new domain, webmasters and site owners generally use 301 redirects (permanent) or 302 redirects (temporary). Redirects tell search engines that the website has moved and to start indexing the new site. Recently search engines have recommended using a canonical tag to redirect them to your new domain.
Canonical tags are easier to implement than 301 or 302 redirects because they do not require anything to be done on the server side and only redirect search engines not visitors. They are considered as “strong hints” to search engines and are not as authoritative as 301/302s but as time progresses they are expected to become authoritative. Canonical tags are implemented by entering them into the header HTML of the page that you want to redirect. This technique used to only work within a domain to move pages, but it can now be used to move pages to a new domain or to move whole domains.
When I read about their new cross-domain capability the first thing I thought about is how canonical tags may be misused similar to the way that redirects are sometimes misused.
One of the most common misuses for 301 redirects is faking pagerank. Some sites use 301 redirects to make it appear as if their site has a higher pagerank than it actually has. They accomplish this by setting up a 301 redirect from their site to a site with legitimate pagerank. When users view the site with fake pagerank they see the pagerank coming from the site where the 301 points. Fake pagerank is generally used by people who want to sell links or the domain.
It is not hard to check for fake page rank. There are lots of free tools out there, but it is simple to do manually. Basically, you want to check for the cached version of the site. One way to do this is by typing info: domain name into search engines. If the site that appears in the search results is not the domain name that you entered, the pagerank is fake. This brings us to canonical tags.
I have recently read about a few misuses of canonical tags. The first one was about a site using a canonical tag to redirect search engines from the page within their domain that they had their links on to their homepage. People who placed reciprocal links on this site were under the impressions that the page that their links lived on had pagerank. When in fact, not only did the page not have pagerank but due to the canonical tag this page will be never by search engines.
Another incident involved hacking. A site was hacked and a canonical tag was entered into the HTML code and pointed to a spam site. In this instance, the canonical tag was used to make it appear that all of the legitimate site’s content was originated by the spam site. This tactic devalued the legit site while adding significant value to the spam site.
Misuses of canonical tags can be checked by implementing the same method that I described for checking 301 redirects. However, you can verify that it is a canonical tag and not a redirect by clicking on View in the toolbar bar and then selecting Page Source. Look at the top of the page in the <head> for the rel="Canonical" meta tag. Next, scan the rest of the page for the tag. Even though it is meant to be placed in the <head> it could be placed in the body. Google says that they do not trust canonical tags in the body, but it is still worth investigating. The second scenario where tags were misused leads me to believe that it is a good idea to periodically view you own site’s source code to make sure a canonical tag has not been added.
As technology continues to evolve there will always be individuals looking to take advantage of it. The best defense is to stay engaged. Staying up to date and understanding how to correctly implement new technology will help you to understand how it may be used against you.
