Google certainly wasn’t the first search engine on the Internet. But Google did it better and provided truly useful search results. Since that day, Google as a company has never stopped expanding.
While SEO is performed for all search engines today, the primary search engine that handles the majority of the Internet's traffic is Google. Whenever we talk about SEO, people automatically assume we're talking about optimizing a website for Google.
When it comes to SEO, there are many factors we need to check, both on-site SEO and off-site SEO. But if your on-site SEO is not up to par, then no matter how good your off-site SEO is, you won’t get the expected results.
For starters:
- What is Google crawling and indexing
- Importance of Keywords in SEO (Beginner’s Guide)
- How to get organic traffic from search engines
I checked a website I was working on for SEO and discovered that it had some serious issues related to canonicalization. I quickly fixed the issues and decided to write an article explaining what canonicalization is and how to properly canonicalize a website.
What is URL Canonicalization?
The word "normalization" can be difficult to understand. I will try to explain it in simple terms.
Suppose a website has two URLs:
- http://thewebpage.org
- http://www.thewebpage.org
Both pages display content, but neither redirects to either page. This can cause duplicate content issues with Google and could expose you to a penalty.
Let's look at another example. There are two URLs on a website that resolve to the same page.
- http://thewebpage.org
- http://thewebpage.org/index.php
If both web pages show the same results, this could also cause problems!
You may not pay much attention to this issue, but this can lead to a serious duplicate content penalty. The problem with search engine bots is that they can't decide which version of a URL should be added to the index. If two pages resolve to the same content, they will assume that one is a duplicate of the other, causing your site to be penalized.
If your website opens on two URLs showing the same content, you have to fix this problem. You have to use server settings so that the website opens on one of the versions regardless of whether the user opens with www or not. In this way you can fix the canonicalization problem.
Sometimes you may want to share the same content on two URLs, then you can use the rel=”canonical” tag to let search engines know which is the original content and which is the copy. This can prevent you from getting a duplicate content penalty.
How to properly apply URL canonicalization?
Now let’s look at how to apply URL canonicalization. We can do it without typing multiple lines of code. A simple rel=”canonical” tag is enough to achieve canonicalization.
* Savings
For example, there are two URLs on the website that return the same content after parsing. The two URLs are:
- http://thewebpage.org
- http://thewebpage.org/index.php
HTML Normalization
The second URL has the same content as the first URL. They both display the same page, so you can apply the rel="canonical" tag, which in this case indicates that the URL containing index.php is the canonical URL for the first URL.
Here is how it is applied.
<link rel=”canonical” href=”http://thewebpage.org/index.php”>
HTTP header normalization
The above tags work for HTML content, but what if we are dealing with non-HTML content, such as PDF documents? In this case, we can use HTTP header normalization.
> HTTP/1.1 200 OK
> Content-Type: application/pdf
> Link: <http://www.example.com/white-paper.html>; rel=”canonical”
> Content-Length: 785710
[](http://googlewebmastercentral.blogspot.de/2011/06/supporting-relcanonical-http-headers.html)You can get more information about HTTP header-based canonicalization on the Google Webmaster Blog .
When should you use normalization?
Now that you understand what normalization is, let’s move on to the topic and see when you should use it. Because there are many other cases besides the two I mentioned above.
Here are a few situations that can be prevented with proper URL canonicalization.
- Multiple different URLs for the same content
- Different categories and tags lead to the same content
- Mobile site showing the same content but on a different URL/subdomain
- A URL that has both HTTP and HTTPS URLs and both produce the same content
- Various ports
- When the website has a www version and a non-www version
- If you share syndicated content
These are some of the main conditions where we can apply URL canonicalization to avoid our website from facing any kind of duplicate content penalty.
You should not be performing URL canonicalization at this time!
There are some cases where we should not perform URL normalization and this section of the article aims to explain those specific cases in detail. You can also consider these cases as errors in the URL normalization process . Let me list these cases one by one and try to explain most of them in a very simple way.
Skip paging normalization
If you are planning to canonicalize paginated URLs, then you should know that this is a very bad idea. You should not add a canonical tag to the second page of URLs because that URL will not be indexed by Google at all.
Multiple Canonical Tags Are Bad
If a page has multiple rel=”canonical” tags, this can be very harmful to you. Please specify a specific tag and clearly state which one you prefer.
[Tweet “Don’t add the Canonical tag to shortened URLs”] I’ve seen a lot of people apply the Canonical tag like this:
<link rel=”canonical” href=”index.php”>
This style of canonicalization can easily lead to a lot of mistakes. You need to understand that the more complete your canonical markup is, the better it is for you and your content.
<link rel=”canonical” href=”http://thewebpage.org/index.php”>
The above markup is a better way to apply normalization.
[Tweet “Don’t use canonicalization just for the sake of localization #SEO #Google”] Localization means targeting and manipulating your website content to serve users based on the region they visit. If you really want to create a better website for a global audience, you can read Google’s guide to creating a multilingual website .
Mobile version of the website
It’s not enough to just use the canonical tag to differentiate between mobile sites on subdomains of your main site. Google recommends that you use both rel=”alternate” and rel=”canonical” to indicate that the URL is for the mobile version of your site.
Here’s how to do it:
> <html>
> <head>
> <link rel=”canonical” href=”http://example.com/” >
> <link rel=”alternate” href=”http://m.example.com/” media=”only screen and (max-width: 640px)”>
> </head>
> <body>
Do not use the Canonical tag outside of a
Search engine bots will completely ignore tags set outside of the site area, so in order to apply the proper canonical tag you need to add it between.
Do not use multiple canonical tags on a single site
There is no point in using multiple canonical tags. Search engines will ignore both tags and you will face strange SEO behavior and problems. Multiple canonical tag URLs are sometimes caused by plugin glitches, so you might want to keep an eye on that.
Don't point your canonical URL to a site with a non-200 status code
Websites with 301 and 302 codes force search engines to crawl an additional URL, which means they need to crawl two URLs at the same time. This can add up very large and easily eat up your crawl budget.
A URL with a status code of 404 is a complete waste of crawling and search engines will completely ignore your tags.
Don't use canonicalization to shape PageRank
PageRank is no longer a public entity or statistic for a website, but search engines still take it into account. If you are planning to use the Canonical tag to boost PageRank for better rankings, I must make it clear that this will do more harm than good to your website.
Final Words
The concept of on-site SEO is much more complicated than you think. You need to handle many things at the same time and keep an eye on the changes that happen every day.
- Read next: How to use rel=canonical for content syndication and SEO
- Read more about URL normalization later
This post is intended to show how to apply canonicalized URLs on your website. Keep in mind that canonicalization is a delicate process and can harm your website if not done correctly. Manage your website properly and make sure canonicalization is performed correctly.
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