Canonical tags are a technical solution used to tell the search engines the original or the master copy of a page. This helps to prevent duplicate content issues. The definition of canonical URL is ‘the best representative page from a group of duplicate pages’.
If the canonical URL is not used then the search engine may penalise the website for duplicate content. As the website grows and new pages are added canonical tags become an important SEO item. Canonical tags can be used to tell the search engine which version of the page to index.
Using canonical tag
The canonical tag is used to specify a canonical URL and is placed in the head section of a page. It is an HTML tag and is also called ‘rel=canonical’. It will look like
link rel=”canonical”, href=”http://www.chosenurl.com”
The URL enclosed within the ‘href’ attribute is the canonical URL.
All your pages should have canonical URLs on them and some can be self-referencing if there are not any variations.
Most content management systems (CRM) provide a field on each page to add the canonical URL. They can be easily added without the help of a developer.
Where should the canonical tag be specified?
The canonical tags can be set in several ways. The different methods are as follows:
- HTTP header
This method gives you complete control to tell Google which page should be indexed as a canonical URL. This is the most preferred method. To use, just add the ‘rel=canonical’ HTTP header response to the pages you want to show in the search results.
- XML Sitemap
The sitemap tells Google that each page has to be indexed but leaves it to Google to determine which pages are duplicates and which are canonical URLs.
- 301 redirects
When you create a 301 (permanent) redirect, Google will interpret it as canonical. However, once the redirect is used only the redirected URL will be visible to the users.
How do canonical tags help in SEO?
The canonical tags can help search engines understand your website better. When you tell Google which pages have to be crawled it becomes easy for it to index your website as a whole. An accurately indexed website tells search engines that you are good at maintaining your website and this will benefit your rankings.
The canonical tag can be used to specify which URL you want your users to see in the search results.
This tag can be used to help search engines consolidate the information they get from multiple URLs into a single and preferred URL.
This tag can be used to consolidate the metrics for a single web page, product or topic.
When you share syndicated content on other websites then it helps you to ensure that your preferred URL appears in the search results.
This tag can be used to ensure that Google crawls the new and the updated version of your pages rather than the two versions of the same page.
- When you specify a canonical URL use the absolute, lowercase URL of a page rather than the relative path.
- To canonicalise the pages do not use the ‘robots.txt’ file.
- The URL removal tool should not be used for canonicalisation. The tool will remove all versions of the URL from the search.
- You should not canonicalise two different URLs that point to the same page by using different methods. For example, If you specify one URL using the sitemap then you should not apply the tag on the same page and specify a different URL.
- To prevent Google from canonicalising a page do not use ‘noindex’ tags.
- The canonical tag should be used while using the ‘hreflang’ tags. You should specify the canonical page in the same language or the most suitable language if the canonical tag does not exist for the same language.
- Use the canonical URL when linking internally. Linking to the canonical URL will help Google understand your preferences.
- Use the HTTPS protocol whenever possible as Google prefers this protocol.