Links are fundamental to how the internet works, by creating connections between all the disparate documents on the web. Internal links are connections between pages on the same website, and internal linking can have a huge impact on the ranking ability of a given URL.

This article will explain how internal links can help search rankings, and how issues with links can have the opposite effect. Throughout the article you will find links to all the relevant Hints that Sitebulb uses.

The value of internal links

Most everyone in the SEO industry understands the power of backlinks from other websites (inbound links), which count as 'editorial votes' for a URL in the eyes of search engines.

One of the things that set Google apart, when they first came on the scene, was their calculation of a URL's relative value based on incoming links, through their PageRank algorithm.

PageRank Formula

Since then, 'link building' has been big business, with SEOs taking various approaches to creating links back to their pages from other websites. However, since the PageRank algorithm is URL-agnostic, you can 'manipulate' the search engines in a similar way by adjusting your internal links.

So if you have a page for which you have spent a long time creating fantastic content, and you think it has a great chance to rank for lots of keywords, you can increase the PageRank of this page and give it a better chance to rank by pointing more internal links at it. This will complement any external backlinks you develop to this page.

Internal link optimization represents one of the most effective on-site optimization techniques, and you can make big gains in organic search by improving internal linking.

Power of internal links

Image shared by Andy Drinkwater of iQ SEO.

In the field of SEO, a 'canonical', is a way of indicating to search engines the 'preferred' version of a URL. So if we have 2 URLs that have very similar content - Page A and Page B - we could put a canonical tag on Page A, which specifies Page B as the canonical URL.

To do this, we could add the rel=canonical element in the <head> section on Page A; 

<link rel="canonical" href="" />

If this were to happen, you would describe Page A as 'canonicalized' to Page B. In general, what this means is that Page A will not appear in search results, whereas Page B will. As such, it can be a very effective way of stopping duplicate content from getting indexed.

When you set up a canonical, you are effectively saying to search engines: 'This is the URL I want you to index.' People may refer to a canonical as 'a canonical tag', 'rel canonical' or even 'rel=canonical'.

In Sitebulb, if a URL is canonicalized, it is also classed as 'Not Indexable.' Conversely, if a URL has a self-referential canonical (i.e. a canonical that points back to itself) this URL would be Indexable.

Self-referential canonicals are a useful default configuration, and are typically set up to help avoid duplicate, parameterized versions of the same URL from getting indexed, for example:

Canonical setup Hints

There are 2 Hints that relate to the basic set up of canonicals:

  1. Canonical points to a different internal URL
  2. Canonical points to external URL

How are canonicals implemented?

The most common way that canonicals are implemented is through a <link> tag in the <head> section of a URL. So on Page A, we could specify that the canonical URL is Page B with the following:

<link rel="canonical" href="" />

Canonicals can also be implemented through HTTP headers, where the header looks like this:

HTTP/... 200 OK

Link: <>; rel="canonical"

Typically, this is used to add canonicals to non-HTML documents such as PDFs, however they can be used for any document.

As such, it is considered best practice to only ever use one method of assigning canonicals for each URL on a given website.

Canonical implementation Hints

There are 5 Hints that relate to the implementation of canonicals:

  1. Canonical tag in HTML and HTTP header
  2. Mismatched canonical tag in HTML and HTTP header
  3. Multiple canonical tags
  4. Multiple, mismatched canonical tags
  5. Canonical only found in rendered DOM

Canonical issues

Issues with canonicals can be a massive problem for SEO, since canonicals affect indexing, and if your pages are not indexed then they have no chance of receiving search traffic.

There are a range of different things that can go wrong with canonicals, and Sitebulb's Hints will highlight all of them. We've split them out into different types below.

Implementation issues

There are 3 Hints that relate to implementation issues - problems with the code or how the canonical has been configured:

  1. Canonical is a relative URL
  2. Canonical is malformed or empty
  3. Canonical outside of head

Mismatched protocol issues

There are 2 Hints that relate to mismatched HTTP/HTTPS canonicals:

  1. Canonical points to HTTP version
  2. Canonical points to HTTPS version

Issues with the canonical URL

There are 9 Hints that relate to canonical URL itself:

  1. Canonical points to another canonicalized URL
  2. Canonical loop
  3. Canonical points to a redirecting URL
  4. Canonical points to a disallowed URL
  5. Canonical points to a noindex nofollow URL
  6. Canonical points to a noindex URL
  7. Canonical points to a URL that is Error (5XX)
  8. Canonical points to a URL that is Not Found 404
  9. Canonical URL has no incoming internal links

Pagination issues

There are 3 Hints that relate to pagination and pagination canonicals:

  1. Paginated URL missing next/prev canonicals
  2. Next/Prev Paginated URL is canonicalized to different URL
  3. Noindex found on rel Next/Prev Paginated URL

Further Resources & Reading

This guide is intended to be an accompaniment to Sitebulb's Canonical Hints. For any of the Hints listed above or found in the software, you can click through to the specific Hint and find out more details about what it is, what triggers it, and what you can do about it.

There are also plenty of excellent 3rd party resources that can help you further with understanding canonicals and what you might do to fix any issues:

URL is orphaned and was not found by the crawler
Pagination URL has no incoming internal links
Alternate URL has no incoming internal links
Only receives nofollow links or links from canonicalized URLs

Has only one followed internal linking URL
Has no outgoing links
Has an internal link with no anchor text
Has an anchored image with no alt text
Has incoming followed links that do not use descriptive anchor text
Has one or more outgoing followed links with non descriptive anchor text
URL receives both follow & nofollow internal links

Has link with a URL referencing LocalHost or
Has link with a URL referencing a local or UNC file path
Has link with a URL in onclick attribute
Has a link with an empty href attribute
Has a link with no href attribute
Has a link with whitespace in href attribute
Has outgoing links with malformed href data
Has link to a non-HTTP protocol

Ready to try Sitebulb?
Start your free 14 day trial now

Start Free Trial