Canonicalisation is an important concept to understand when it comes to optimising webpages for better search engine rankings. It has become increasingly important due to the proliferation of web technologies, like smart phones and tablets, that require webpages to be rendered differently for different devices. Canonicalisation, sometimes referred to as ‘Canonicalization’, can help ensure that all versions of a webpage are properly indexed, and that search engines properly index the most important version of a page. The goal of canonicalisation is to focus link equity (ranking power) on one preferred version of a page, so that search engines know how to properly interpret incoming links.
What is Canonicalisation?
Canonicalisation is the process of informing search engines which version of a page to index and serve in the search results. This can be achieved through a simple web page instruction, the ‘Canonical’ tag. This tag helps search engines understand the intent of a webmaster which version of the page should be indexed in the Search Engine Result Pages (SERPs) when a query is formulated. Canonical tags can be used to consolidate pages that have duplicate or similar content and to inform search engines about the original source of content when there are multiple copies of the same content existing in different places on the web. Canonicalisation helps to avoid mischievous issues like scrapping or content duplication, and it allows webmasters to define the main URL when there are a variety of URLs that head to the same destination.
When Should You Use a Canonical Tag?
Canonical tags should be used when there is more than one version of a page. When multiple versions of a page are available, search engines may experience confusion regarding which version should be indexed and so they will try to decide on the most relevant result based on their algorithms. However, by using a canonical tag, you can tell the search engine which version of the page should be indexed, thus avoiding any confusion.
A few common scenarios where a Canonical tag should be used include:
• URLs that use parameters that repeat the same content in different orders (for example, a dynamic product page that uses session IDs).
• Multiple URLs with the same content (for example, a page available under both http:// and https://)
• Cross-domain duplicate content (for example, when a single page is shared across multiple websites)
• Content that can be reached through multiple URLs on the same website (for example, pages with multiple URLs due to certain CMS systems)
How to Implement Canonicalization
You can implement canonicalization following the below steps.
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1. Identify the version of each page you wish to be indexed: This is the page which you want visitors to land on and is often referred to as the “canonical URL”.
2. Determine any additional versions of the page: Whenever a search is triggered for an existing page, additional versions of the same page, such as mobile, are created for the search engine’s convenience.
3. Add rel=canonical tag to the additional versions: This is a tag that you add to the HTML head portion of additional versions of the page. It essentially tells search engines to index the canonical URL instead. For example, if you have a blog post that lives on both http://www.example.com/blog/post and www.example.com/blog/post.html, you would include the tag on the version of the page with the .html extension.
4. Add self-referencing canonical tag to the canonical version: This is essentially an additional step where you will also include the rel=canonical tag on the canonical version that contains the same URL as the one specified in the tag. So in this example, you would also include on the original URL with no file extension at the end.
General Guidelines and Best Practices for Canonicalisation
1. Implement a single canonical tag for each page: You should not implement multiple canonical tags per page as this can result in confusion in the eyes of search engine bots.
2. Avoid canonicalizing redirects: If a page redirects, then you should be careful when making it canonical. A canonical tag will help in consolidating link equity, however it could also potentially create a loop where the redirected page is always steaming to itself.
3. Don't canonicalise all URLs: You should take care with canonicalising homepages and other important URLs such as product pages. If you set a homepage to be canonical to the URL of a related web page, you could be inadvertently sending the link equity and rankings of the homepage to that other URL.
4. Don't canonicalise URLs that differ significantly: If two URLs differ significantly, e.g. one is a product page and one is a blog post related to that product, you should not canonicalise them to each other. This can cause confusion and also prevent them from being properly indexed.
Conclusion
In conclusion, canonicalisation is an important concept to understand when it comes to optimising webpages for better search engine rankings. When there are multiple versions of the same page available, or when the same content is present on multiple URLs, it’s important to implement a canonical tag to ensure the correct version of the page is indexed by search engines. Following the general guidelines and best practices outlined here can help to ensure that a website is optimised to perform well in the SERPs.