Canonical URL (or Canonic Link) is a way to show search engines that similar URLs are actually the same. This is important for websites that have products and content that are available from several different addresses. A canonical URL means that duplicate content does not affect your ranking and allows your linking power to go to the right landing page.
What is rel = canonical?
Rel = canonical is the HTML element that helps you handle duplicate content issues on your site. If you have multiple pages with the same content, you can use rel = canonical to specify which one is the main page. You simply select one of the variants and make it the primary by putting a canonical URL on the other pages that point back to the primary page.
What duplicate content?
Perhaps you think this with duplicate content feels a little strange, who would upload two exactly the same pages? But the fact is that it is actually more common than you think. In many cases, it happens completely automatically in your Content Management System (CMS) and it is usually common in online stores that have products in several article groups / categories.
Canonicals can refer to itself. It does not matter if the canonical link on a landing page refers back to itself. Some CMS, such as WordPress, adds canonical back to itself automatically upon publishing.
Avoid sending mixed signals If you do not use canonical links correctly or if you send mixed signals, search engines may ignore your canonical. Do not create long chains with canonical links: A> B, B> C, etc. It only creates a loop and will not be effective at all. Well, instead, a page and write all the canonicals to that page. The same applies if you canonicals returns to the first page: A> B, B> A; or redirects back to the first page: A> B, B> 301> A
Be careful with canoniclas on almost identical pages. Most of the time, you think about exactly the same pages when talking about canonicals. But in some cases almost identical pages may also be in need of a canonical. But be careful! If the search engines think they are too different, they ignore your canonical link anyway.
Only one canonical per landing page If there is more than one canonical URL on a landing page, the search engines will ignore all canonical links, so make sure you only add one per page.
Canonical vs. 301 redirect
In many cases, a canonical works just like a 301 redirect . It determines a primary side and over linkage. But these two tags give two completely different results. The Canonical link allows you to stay on the same page as you entered but link power etc. goes to the primary page and that is also the one found in the search engine index.
A 301 redirects you directly to page B without even seeing page A. This means that you can not see traffic coming to that URL because no visitors ever land on that landing page. With a canonical you can continue to see visits to both landing pages. The effect that is right depends entirely on the circumstances of your site.
Canonicals across multiple domains
If you manage multiple domains and use the same articles in several places, canonicals can help you avoid duplicate content. It can also be helpful when publishing another person's article in its entirety on its own site (of course with permission). It is common for guest posts or the like, which gives your site a good content that favors your readers while all linking power goes to the one who actually wrote the article.