As a leading SEO services provider, we often get inquiries regarding proper utilisation of canonical tags and 301 redirects from our clients. On the other hand, we often see how things have gone wrong with websites when these duplicate content handling methods have not been used correctly.
While similar in their intent, 301 redirects, when compared to rel=canonical tags, are completely different in their purpose. With that said, there is no universal approach when it comes to using them, and it is always recommended that each website is treated individually.
First of all, let us look at the definition of redirects and canonical tags briefly.
So What are 301 Redirects?
The HTTP response status code 301 means a certain webpage, website or content has been moved permanently, redirecting both users and search engines to the new location where they have been moved. Search engines follow the 301 directive and index the new location, while the old one drops off index over time. While arguably some of the link juice is being lost along the process, relevance and authority are still being passed through the 301 redirect.
What About Canonical Tags?
Canonical tags are used to indicate where the same piece of content is accessible from different URLs and eliminate potential duplicate content issues. They have absolutely no effect on website visitors and only serve as a reference to search engines.
What is the Difference?
Well, itâ€™s a significant one actually.
Search engines follow the 301 directives and mark where the new web document has moved, while completely de-indexing its previous location.
With canonical tags on the other hand, search engines determine whether to respect or completely ignore the canonicalisation request, as it is just a recommendation and not a directive.
Even though regular website visitors will not be able to tell the difference, 301 redirects are transferring users to an actual new web location, while canonical attributes make absolutely no difference as to how a web document is being displayed to users, and all duplicate versions are available to see.
When to Use 301 Redirects
Permanently moving domains
Whether we have acquired a new domain for branding purposes, or we are completely re-branding our existing one, a 301 is the only correct option to indicate which is the right website to be used.
Multiple versions of home pages
We often see major duplicate content problems with multiple versions of a home page.
Some common variations could include:
- www or non-www version (http://www.mywebsite.com or http://mywebsite.com)
- trailing slash (www.mywebsite.com or www.mywebsite.com/)
- different CMS extensions (www.mywebsite.com/home, www.mywebsite.com/index.html, etc.)
Stick to the correct version of the home page you will be using and point all other existing URLs to the correct one via 301 redirection.
Expired content and 404 pages
No visitors want to land on a page that does not exist anymore, or is out of date. In case you decide to completely update an old piece of content, it is recommended to move it to a completely different new location. Use 301 redirects to also point pages with HTTP status code 404 to the most relevant existing ones which are unlikely to change.
Changing URL structures
Whether the content management system has been updated, or if you are testing different URLs for click through rate testing purposes, it is highly recommended that any change is redirected to the correct location with a 301 attribute.
When to Use Canonical Tags
When 301 is not applicable
Many times 301 redirects may not be applicable. This could be due to CMS or server restrictions, or even due to lack of knowledge since canonical tags are much easier to implement, while 301 redirects require server side adjustments.
Accessing same content from different URLs
If a web page or document is accessible from more than one URL, canonical tag implementation is required to indicate which version should be preferred as indexable. This is especially valid for e-commerce websites where products may appear under different categories or filters.
In cases when a web document is broken down into different pages, canonical tags should be used to point to where the full version of the content is located.
The tricky part here is actually ensuring that there is an existing version displaying the whole content. For example, if a web store has five paginated listings of a certain category (www.mywebsite.com/sale/?page_id=2..3,4,5), then each one of them should have a canonical tag pointing to the page where absolutely all products in this category are displayed (e.g. SEE ALL page). Otherwise certain paginated listings may not be indexed at all. In similar cases, when content is not displayed in one single page, a “rel=prev/next” attribute would be more suitable to utilise.
If for some reason you syndicate content on your website, thanks to cross-domain canonical support you are able to point back to the original version of the web document you are quoting.
Dynamic & PPC landing pages
Dynamic URLs can be generated on each website visit, for example for tracking purposes. In general, there is no reason to have these dynamic URL parameters indexed, hence indicating the original preferred indexable version with canonical tags is advisable.
In a post-Panda world, where eliminating duplicate content occurrences is of great importance, proper knowledge of 301 redirects and canonical tag utilisation is a must.
As you can see, both methods serve the same purpose but are completely different in their nature and application. While it may not really sound that complicated (and it is quite simple indeed, as long as you follow the basic logic), a word of caution is needed here. If not used properly, 301 redirects and canonical tags CAN and WILL cause much more harm than good.
In cases like 301-redirecting all website pages to the home page, 301-redirecting an existing 301 redirect, or sporadically spreading canonical tags across all pages and so on, is likely to leave your website sidelined for quite a while. And no one wants that, right?
Choosing how to use 301 redirects and/or canonical tags will be determined by the particular occasion, as one may not work well in some cases and vice versa. If you are not completely sure about your website, we are always happy to help.