5 ways to accidentally create canonical issues

It can be easy to publish duplicate content and create SEO issues. How does the use of a canonical tag help overcome these traps?

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Canonicalisation is a word that is highly unlikely to pass the lips of most people.

In SEO parlance, however, it is an important one and canonical issues can be damaging to SEO performance. There are some traps that are actually very easy to fall into and I want to share some of the more common issues that you may not realise are affecting your site.

What is a canonical issue?

Canonical issues are really duplicate content issues, but with a fancy name. Duplicate content is where there are multiple instances of a webpage available on multiple URLs. This could be across multiple domains but it is an issue that can occur on a single site. E.g. if a product is available in multiple categories on an e-commerce site, the product description / images / etc will be replicated across multiple URLs.

Search engines see this as duplicate content and they do not like it. No search engine wants their results pages filled with identical web pages, so they will typically choose one instance of the same content and ignore others. This ‘master’ version is known as the canonical version and you can use canonical tags to help guide the search engines.

Many talk about duplicate content penalties, but I prefer to refer to it as a duplicate content filter – the search engines will ignore duplicate content in favour of one ‘canonical’ URL.

Why do we care?

There are a number of reasons you need to pay attention to canonical issues on your site.

Firstly you may prefer one URL to be shown in SERPS over another – particularly if one looks user-friendly and nice and clean, versus another that is very code based or complicated. By using canonical tags, you can be in control of which URL is chosen as the master.

Link juice… Now I’ve got your attention – you do not want to undo all your hard link building work do you? Without using canonical tags, you risk diluting the value of links that point at multiple versions of the same content.  This means the link juice for all the duplicate pages is amalgamated, which is beneficial for search rankings.

If you have competing URLs, it’s more complicated to track metrics such as sessions, visitors, or engagement across all pages. Setting up a canonical tag doesn’t guarantee that the other pages get zero visits but it will help skew the traffic towards the one you favour.

Organisations that have multiple sites may choose to upload their content across all of their platforms. There’s absolutely no harm in this from a user point of view but they really should prioritise one site over another for SERP purposes.

Google doesn’t crawl every page every day. Google allocated a crawl budget to each site which determines how often it returns to look for new content and how deep its spiders or bots go into your site on each visit. By using canonical tags, you won’t waste any of this budget crawling duplicate pages.

Here we look at five different types of canonical issues that site owners should look out for. The first two impact the entire site.

1. www vs. non www

Like us, you may have chosen to drop the ‘world wide web’ prefix from your site and just opted for http://domain.com i.e. https://browsermedia.agency/. However, you can’t control what users search for, nor can you update all of your old links. As this is a site-wide issue, it means that every single page of the site would be duplicated unless you have configured your server and redirects correctly. Gulp.

2. https vs http

If your site is secured by an SSL certificate (a type of digital certificate that provides authentication for a website and enables an encrypted connection) then it moves from http to https. However, unless you have ensured that only https is available, you will have created duplicates of every single page.

3. Desktop and mobile websites

In the main, organisations that have separate mobile and desktop sites are few and far between now but if you’re one of them, the same applies. Publishing identical content on both sites will cause the same canonical issue.

4. Dynamic URLs

Content management systems are based on the principle of generating web pages by populating templates with content from a database. The precise way in which this happens will vary and some platforms will use URL parameters to control the content of a page.

If you have content that is published on multiple pages, it can be easy to inadvertently create duplicate content. The use of canonical tags will allow you to point all duplicate pages to one instance of that dynamic URL.

5. Syndicated content

Most PR and content professionals are aware of certain sites that syndicate content. A tactical sell-in to a journalist at a particular news website can mean your content appears in multiple outlets. This is a win from a brand awareness perspective, but does introduce potential duplicate content issues

As long as the journalist hasn’t been promised an exclusive, it is worth asking if a canonical tag could be added to point at the original source (your site).


As ever, Google reserves the right to make its own decisions about the content it serves to users based on what it deems to be their intent. But tagging content as canonical can often steer content in the right direction.

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