What is URL Canonicalization?
What is a canonical tag?
Also known as rel canonical Canonical tags; It is a way to tell search engines that a URL is the parent URL of a page that has multiple copies.Using the canonical tag prevents problems caused by duplicate content appearing on multiple URLs.In its simplest terms, the canonical tag tells search engines which version of a URL you want to appear in search engine results pages.
The part highlighted in red indicates that any page where this tag appears should be treated as a copy of the specified URL.
What is the importance of canonicalization?
Duplicate content is quite complex and can cause a number of SEO issues when search engines detect content that is a one-to-one match or similar to each other. Simply put, when crawling such duplicate content, search engines may miss some of your unique content. Duplicate content can also weaken your ranking abilities. Apart from all this, duplicate content can also cause search engines to choose the wrong URL as the “original”. To prevent all this, you can use canonicalization.
URL issues
You might be thinking, “Why would they duplicate?” This might lead you to believe that canonicalization isn’t a big deal. For example, we humans might think of each page as our homepage. But for search engines, each page is a separate page.
For example, let's say you can access your home page in the following ways:
- http://www.ornek.com
- https://www.ornek.com
- http://ornek.com
- http://ornek.com/index.php
- http://ornek.com/index.php?refer=twitter
To a human being, all of these URLs represent a single page. But For a search engine, each of these are separate pages. In this example alone, you can see 5 different copies of your homepage. And believe me, this was just a small example; we could come up with many more variations.
Modern CMSs (content management systems) make this problem even worse. Many sites automatically add tags, allow multiple URLs for the same content, and add many URL parameters. For these reasons, you can have thousands of duplicate URLs on your site and not even realize it.
Best canonical tag implementations
Repetitive content can be extremely annoying, but there are some important points that can relieve your boredom:
- Canonical tags can point to themselves
A canonical tag is fine if it points to a valid URL. In other words, if URLs X, Y, and Z are duplicates and canonical tag X points to URL X, then that's normal. It may seem a bit confusing, but it's normal.
- Proactively canonicalize your home page
Home page duplicates are very common. Considering that users can also link to your home page in a way that you cannot control, this can cause many unforeseen problems. To prevent this, it is a good idea to add a generally accepted tag to your home page template.
- Randomly check dynamic canonical tags
Using bad code can sometimes result in a different canonical tag being created for each version of a site’s URL. This is why you should make sure to check your URLs, especially for e-commerce and CMS focused sites.
- Don't give mixed signals
Sending mixed signals can cause search engines to avoid or misinterpret a canonical tag. In other words, don’t canonicalize page A to B and then B back to A. Or similarly, don’t canonicalize page A to B and then page B back to A with 301 redirects. It’s also not a good idea to chain canonical tags (A-–>B, B-–>C, C–->D). So send clear signals and don’t force search engines to make bad choices.
- Do not perform canonicalization operations such as duplication
When canonicalizing, most people think about duplicates. However, it is also possible to canonicalize pages with very similar content. So be careful. Although there is a lot of debate on this topic, there is no problem with doing this for currency, location or small product pages that are very similar. However, if the non-canonical versions of these pages are not suitable for ranking or if the pages are very different, search engines may ignore the tag.
- Canonicalize cross-domain duplicates too
If you manage 2 sites at the same time, you can use canonical tags between domain names. Let's say you are a person or company that publishes the same article or news on 5 different sites.By using canonical tags, you can concentrate all the ranking power on just one site. Remember that when you canonicalize, other sites will be blocked from ranking, so you need to make sure that it benefits you when you do this.
Canonical tags vs. 301 redirects
This comparison is a common SEO curiosity, but it’s a trick question and there are cases where both options are justified in their own way.
For example, if you redirect page A to page B with 301 redirects, your visitors will automatically be taken to page B and will never see page A. If you instead associate page A -> page B with a canonical tag, search engines will target B, but people will be able to visit both URLs. You should choose whichever option is right for you.
