Answers for the most frequent questions
The Rel=Canonical tag represents many times just a confusion, for webmasters so as for SEO specialists. Even if Google offers support for implementing this tag, there can many times appear problems of understanding its functionality. Recently, on WebmasterCentral’s blog was published an article that speaks of common mistakes in using this tag.
Down below there are clarifications and answers for frequently asked questions about rel=canonical offered by Dr. Pete:
What is rel=canonical?
The rel=canonical tag represents a way of telling Google that an URL is equivalent with another URL regarding the search. The URL (B) is a duplicate of URL (A) and the canonical tag put in page B towards A is a strong indicator, very much taking into consideration by search engines, indicator that shows how URL A should appear in searches.
The next code line will appear in the page with URL B, section <head>:
<link rel=”canonical” href=”http://www.domain.tld/url-a.html” />
Should Rel=Canonical tag be used for Pagination?
This is one of the most frequent questions. Let’s consider a series of pagination pages (1,2,3,…n). Should page n be canonicalized at page 1? Officially, the answer is no and Google does not recommend this. In exchange, it recommends to have rel=canonical on a “View all” page (in case it is possible to have all the results in one page) or use rel=prev/next.
Can Rel=Canonical be used between domains?
Yes, it can be used. On 15th of December 2009, Google announced its support for using rel=canonical tag between domains, in order to solve the duplicate content issue. Rand Fish has made a test with his blogs. Google fully explains how to implement this tag between domains here.
Should Rel=Canonical be used between domains?
Here things puzzle a bit. First of all, if the pages are too different or using the rel=canonical tag between domains seems manipulative, Google might ignore this method. The ideal situation in which rel=canonical would be used is the one in which more websites that are held by the same person (company, society) share the same content, content that is useful for the users of each website. In other cases it shouldn’t be used. In order to use canonical, the content between domains must be alike.
Should Rel=Canonical be used for pages with similar content?
Although after tests Dr. Pete concluded that rel=canonical works in some cases for pages that are significant different, this does not necessarily mean that it is a good idea to act this way. The best is to keep this rel=canonical approach for duplicates or pages with almost identical content. You don’t need to use rel=canonical instead of 301 redirect. We all know the difference between them , however, being used this way can determine the engine to ignore the canonical tag.
Should Rel=Canonical be used on a canonicalized page?
Many specialists ask themselves if the canonical tag should be implemented on the canonicalized page. Yes, it can, although there are still pros and cons if there is necessary or not, we recommend that every page has the canonical tag implemented towards herself, from various reasons:
- it can happen that a website to have not so defined rules of rewriting of URLs and the content of a page to be accessed from many URLs. E.g.: agilemedia.com/articol-blog-1/ and agilemedia.com/articol-blog-1a/. The natural links can be put in different forms and in the majority of cases they are copy&paste.
- the URLs from certain campaigns that present parameters can be indexed: ?utm_mediu, ?utm_source.
- There can also be comments from a blog that can be indexed. It can have tens of comments on every article and every comment to have a permanent link. E.g.: agilemedia.com/blog-post/ is the original article and the URLs towards comments are: agilemedia.com/blog-post?replytocom123, agilemedia.com/blog-post?replytocom124, agilemedia.com/blog-post?replytocom125, agilemedia.com/blog-post?replytocom126 and so on.
Here the examples can continue and from these reasons we recommend using canonical on every page. Although it is not a difficult technical issue, be careful how implementing rel=canonical.
Is it ok to implement Rel=Canonical on the entire website?
This recommendation was also made by the ones from SEOmoz some time ago, considered a safe approach. However, the excessive usage of the tag can become a problem and determines Google to ignore it. Another inconvenient is the wrong implementation of the tag as we already have discussed earlier in this article. A problem that can appear is when you put canonical on inappropriate pages and that is why you must be careful that duplicate pages be well chosen before the implementation.
In ideal cases, Dr. Pete recommends using rel=canonical on homepage, on pages with duplicate content and on pages with parameters that can create duplicate content.
Rel=Canonical or 301 Redirections?
As I’ve already mentioned, there are two similar approaches, but there are not the same from a SEO point of view. It is quite simple: if you want to fully remove the duplicate content of two pages, use a 301 redirection and if you want to keep both the pages available for visitors and one of them to appear in the search results, then use rel=canonical.
Does the Rel=Canonical tag transmits Authority/Page Rank?
It is a question with an answer that is hard to measure/quantify. If it is used in an appropriate manner, acknowledged by Google, it can action in the same way as with a 301 redirection. There are opinions according to which there is Authority and Page Rank sent to the uncanonicalized URL, with few losses, as in the case of 301 redirections.
Can Rel=Canonical be used in a row?
What do you think happens if we have 4-5 pages and we go from the canonical tag on the first URL to the last one? This means A will have canonical towards B, B will have canonical towards C, C will have canonical towards D and so on. This gets a little complicated and the same happens with redirections in a row. Things have to be a lot easier and we have to help the search engine understand the content on the website, not redirecting it astray.
Using rel=canonical in this manner can be complicated, it can create problems or it doesn’t present any advantage in terms and Page Rank.
We recommend using the canonical tag in a simple manner, as Google indicates us. Moreover, Google, Yahoo and Bing take this tag into consideration and you can prevent many content duplicate content issues.
Are non-canonical pages indexed?
If rel=canonical is acknowledged by Google, then the non-canonical page is not longer eligible for SERP positioning so it will no longer appear in the Index. Implementing the rel=canonical tag should not raise anymore issues, not even for webmasters and nevertheless for SEO specialists, who have all the necessary information available to be used in a right manner and testing its advantages.