Originally posted this on my SEO blog.

There's a lot of heated debate going on about backlink relevance and many unanswered questions that plague newbies and veteran SEOs alike.

Are relevant backlinks more powerful than irrelevant backlinks?

Do we need them?

Should we be seeking them out?

What is a relevant backlink anyway?

How is relevance measured?

And most importantly, what does all of this mean to us as Search Engine Marketers on a practical and actionable level?

I'm going to answer all of those questions in this post.


How does Google measure relevance?

Though they are developing and buying technology that can read and understand the meaning of images and video, as things stand today Googlebots can only properly read words.

The dependence on keywords is also directly related to the way that we interact with Google, we also input keywords.

Therefore all degrees of content relevance are based on the use of keywords, though not exactly in the way that we as humans read.

Google for example can determine site relevance based on the number of times words are used, whether they're used in conjunction with other related words and how frequent these occurrences are over all of a sites indexed pages and URL structure.

We know it does this because this data is displayed within Google's Webmaster tools.

Google can determine a theme for a site based on the use of common keywords.

So what's a relevant backlink then?

There is quite a lot of ambiguity around the term 'relevant backlink'.

Most definitions of a relevant backlink are wrong, incomplete or misinformed.
In reality backlinks are not either relevant or irrelevant, there are only ever degrees of relevance.

This is how the Googlebot will determine the relevance of a backlink.

a) the linking site is of the same theme
b) the linking page is of the same theme
c) the linking paragraph is of the same theme
d) the linking anchor text is the same as the keyword the site/page is optimized to rank for

The degree of relevance is based around the proximity of related keywords to the link itself.

The next obvious question is...

How much difference does each level of relevance count towards the strength of the backlink?

This is where things get interesting, because the rate at which relevance increases down our list is not linear at all, in fact its EXPONENTIAL.

Based on my experience and observation, the break down goes something like this, with relative importance indicated by the percentages.

a) the linking site is of the same theme (2%)
b) the linking page is of the same theme (4%)
c) the linking paragraph is of the same theme (16%)
d) the linking anchor text is the same as the keyword the site/page is optimized to rank for (78%)

Though these figures are arbitrary, the point I'm making is that anchor text relevance is many, many, many times more determinative as an indicator of backlink relevance than site theme, page theme or even paragraph theme.

When we look at the way content creation on the web has evolved, the necessity for backlink relevance to be calculated like this becomes quite obvious....

Namely social media and blogs.

By their very nature, blogs update more frequently than static websites and due to their content creation revolving around the creative output of an individual in all their eclectic glory, theming a blog around a particular niche becomes difficult, moreover, the statistical data of keyword use becomes negligible.

You're just too unique to be categorized

So a backlink from this blog to what I consider to be the "best ice creamery in texas" will be deemed as being a highly relevant backlink, despite the fact that this blog has nothing to do with Texas or ice cream.

I'm just an SEO dude that likes desert, and Google is cool with that.

Would the backlink pack more punch if the whole site was about texan ice cream?

Yes, almost definitely.

Would that impact be negligible?

Yes, almost definitely.

So is it worth going after backlinks from sites that are completely relevant to my niche?

No.

Based on my exponential theory of backlink relevance, I wouldn't bother trying to find sites that are thematically related to your own.

Usually they're you're competitors and they don't like linking to you anyway, and procuring such links is not a good use of your time.

Give it a shot if you want, but its not the most efficient use of your time given the comparatively small benefit it will give you and the effort required to get the links.

If you can get them easily then go for it, but:

Site relevant backlinks are hard, and the additional effort required to get them is NOT reflected in the additional value they add.

Page relevant backlinks on the other hand are pretty easy to get. These can be relevant articles submitted to article directories and blog networks.

These in turn almost invariably result in paragraph relevant links and also usually give you link text relevant links.

So all in all, a good win.

Does this make irrelevant links like profile links useless?

Absolutely not, because what you lack in relevance, say a 22% handicap, you make up for in anchor text relevance and the sheer number of links you build, the speed with which you can build them, the relatively cheap cost, the IP diversity, and the authority based on the strength of the root domain.

So the handicap of the links not being 100% relevant isn't an issue because you can compensate for that in other ways.

So what does this mean for us as SEO warriors?

If someone offers you a site relevant link, take it. But don't spend a lot of time chasing these links.

Use 80/20 logic and focus on getting a mix of anchor text relevant links and page + anchor text relevant links.

Links that are irrelevant at the site level are fine as long as you can choose the anchor text, and you can more than make up for their lack of site relevance by the number you can build and the ease with which you can do so.

Hope this perspective clears stuff up for people wondering about this.

Cheers,

Gavin