Which Keyword Difficulty Checker Is The Most Accurate?

Keyword research is the first part of the affiliate site process. It's the foundation your site lays upon and the concrete that's going to going to define your early successes in SEO.

In the depths of keyword research lies the “difficulty score”. Often times called “keyword difficulty” or “keyword competitiveness”.

Ever keyword difficulty checker is different but generally they're web based and extract data from the same sources. These data sources are the same because not many companies exist that have good metrics for web competition. The keyword difficulty scores are what sets these tools apart when they're all using the same data.

Many of the tools provide guides for assessing keyword difficulty but most of the scores are out of 100. Some say anything below 40 is a good number and others say anything under 10 is a good number. Most of the time these numbers are for brand new sites. Which makes sense because a brand new site doesn't have the weight of an older site. So ranking keywords for a new site is more difficult but the keyword difficulty range is supposed to help you target keywords that you'd be able to successfully rank for no matter how old your site is.

But before we get into that, let's talk about why you even use the keyword difficulty score. It might not be what you're thinking either.

The ONLY Use Case For Keyword Difficulty

In my personal opinion, keyword difficulty only has one job to perform…

To filter results!

When you put in 3 seed keywords into your tool of choice, it could spit back thousands of results. Besides filtering based on words, your next logical step is to filter based on the initial keyword difficulty score.

Here's the catch though:

Keyword difficulty is different for every single tool. No two tools are alike in that manner. They could get the same data from the same sources, but the keyword difficulty scores would be calculated differently.

Without getting too “math-y”, keyword difficulty scores can be created based on weights, averages, logarithmic scales, and much more. I don't think it's ever been mentioned, but I hope these formulas are derived from tests. Not just hunches from the founders.

The Usual Suspects For Data Sources

There are three major sources of SEO metrics that all of the tools generally use.

Data Sources	Ahrefs	Majestic	Moz
Crawled Links	12 TRILLION	1.3 TRILLION	1.3 TRILLION

1) Ahrefs: Big Crawler With 4.6 Billion Keywords

Ahrefs claims to have the biggest collection of backlinks, boasting 12 trillion known links and updating every 15 mins. This leads to crawling 6 billion pages a day and storing 4.6 billion keywords in its database.

Those 4.6 billion keywords are only available in Ahrefs own keyword tool though. Third parties can only extract data such as Ahrefs Rank, Domain Rating, URL Rating, etc through the API.

2) Majestic: Not Just Fresh Data, But Historical Too

Majestic has two main indexes, a fresh one that updates every 90 days and a historical index which holds all the links they've ever crawled.

At this moment in time, Majestic's bot has crawled 374 billion pages within their fresh index and 1.3 trillion stored within their historical index. Majestic differentiates between unique URLs they've crawled and also the unique URLs they've found. I'm not sure why, but they like to tell us the potential they could have crawled or will be crawling next time.

From a quick look, it looks like Ahrefs has stomped Majestic. I believe Majestic's crawled links of 1.3 trillion URLs in its historical index is equivalent to the 12 trillion known links from Ahrefs index.

3) Moz: The Original Search Gangster

Moz is the originator of the keyword difficulty score. They were the first to coin the term and add a proprietary formula into their keyword explorer.

Moz has received a lot of flack lately because their open site explorer tool doesn't have quite as many updates as their competitors but from what I can see on their updates page, they're doing it monthly or bi-monthly.

A lot of people still use Page Authority and Domain Authority in quickly assessing a pages authority. Whether it's a good idea or not to use it, again, it's just a starting point but we'll have a better idea by looking at the test results.

You'll also see that one of the tools below recently switched away from Moz metrics to providing Majestic metrics.

One final note is this:

Page Authority and Domain Authority are calculated using other metrics that Moz has put together. Which means it's nearly impossible to figure out the keyword difficulty formula for tools that use PA and DA as inputs.

Most software business have many API connections, however this of course is a weakness in their tools as well since they don't have control over inputs.

How Keyword Difficulty Is Calculated By The Most Popular Tools

None of the keyword tools we examine will provide the complete formula for their scoring because 1, it's proprietary to their business and 2, it's probably really hard for us to calculate on our own.

So let's get started with what we know for sure and then see the results of our test.

1) KWFinder (by the way, they gave us a discount here):

KWFinders Low Competition Score is Considered Below 40.

They rely on Moz and Majestic data to formulate their keyword difficulty score.

This is their basic process in formulating the KD score:

1. Analyze results on 1st page
2. Look at the Moz link profile
3. Include Domain Authority
4. Average Out The Values Above

The first step is probably the vaguest, but here's a screenshot of a response from their own blog post. Read our KW Finder Review while you're here.

2) Ahrefs Keyword Explorer

The Low Competition Score In Ahrefs Is Considered Anything Below 40

Ahrefs has a unique scoring system in which they only take links into consideration. From their research, they've seen no correlation with on-page tactics (these days) and the ability to rank higher. Maybe I'm a bit more old school, but that does make me somewhat uncomfortable.

However, I know Ahrefs knows how to run proper tests and have the data to back up their claims.

Very simply, their process is:1. Look at the top 10 results2. How many links are pointing to each of those pages3. How many links are pointing to each of those sites

They don't take into account things like the keyword being in the title, their own proprietary “Domain Rating” score, or any other on-page factors.

Here's a snapshot of what they've mentioned about keyword difficulty

3) Long Tail Pro

Long Tail Pro Considers Low Competition To Be Below 40

An old favorite of mine. They had some hiccups since the business was taken over by new owners and from moving their software to a cloud version, however, that's business and they need to do that sort of stuff in order to keep growing.

In any case, Long Tail Pro switched from Moz metrics to Majestic metrics mid-2016. This was a hard decision I'm sure but you can read more about that decision on Spencer Haws blog.

Long Tail Pro did release guidelines for numbers to follow with these new metrics and they happened to mention a bit about how their “keyword competitiveness” score was calculated

Another thing that's interesting is that they gave their old keyword competitiveness formula out in greater detail

As you can see, if we pull out the old Moz metrics and replace them with Majestic's Trust Flow and Citation Flow metrics. Then we might have a better idea. But as I mentioned above, there are so many factors beyond just the simple formula that they provide.

The fact that Long Tail Pro and KWFinder use third party metrics into their formula means they have less control over the results of their Keyword Difficulty/Competitiveness scores. If Moz or Majestic wanted to readjust the way they calculate PA/DA/CF/TF then it could seriously shift the scoring in these two tools.

4) Moz's Keyword Explorer

Moz Considers Low Competition In Their Keyword Explorer To Be Below 35

Rand Fishkin recently answered a question on the Moz forum about what a “good” keyword difficulty score would be. Within that comment, he gave us an inside look into how the score is composed as well.

Here's the quick breakdown:1. The Page Authority is taken as the constant2. Everything else is the modifier, including Domain Authority, the use of the query, click through rates and more.

Here are two photos, one of Rand's response and also what the official sales page for the Keyword Difficulty tool says

Which Keyword Difficulty Score Can You Trust?

First off, I just want to mention that this test isn't perfect. But it's good enough for us to evaluate the different keyword difficulty scores offered by these tools.

This test was composed of 3 different articles from our Aged sites that are all in different niches. We gauged their performance to the date of this article Sept 14 2017. All 3 were chosen because of their recent performance out of the dozens that we produce for these sites. But what we wanted to know was which one of these was the best predictor of an attainable keyword.

Meaning can you get into the top 10 if they keyword difficulty score says you can. Obviously, there are other factors at hand, but what we're testing for is this one metric offered by these different tools.

The Most Accurate Keyword Difficulty Score

The best correlation with our test articles was with Ahrefs' keyword difficulty score.​

As I mentioned above, their system works purely on backlinks so it's a bit different. Most of the keyword tools allow for around 25-35 as a good score, but Ahrefs window is much smaller. Only going up to 10 for a good keyword. In any case, their competition score of 0 for our best performing article is likely not coincidence.

The Second Most Accurate Keyword Difficulty Score

KWFinder came into second place with lower keyword scores that correlated with our best performing articles. We just wrote a review on KWFinder with some interesting points of view. Not all positive, but after these tests – I am leaning more and more towards moving to this tool completely. Also, the price difference between Ahrefs and KWFinder is pretty big. KWFinder is much cheaper and it seems that the KD score is still very accurate compared to Long Tail Pro and Moz's Keyword Explorer.

Third Place In Our Keyword Competitiveness Test

Next up is Long Tail Pro. Unfortunately, 2/3 Keyword Competitive scores were high enough to the upper part of the range (highlighted in yellow) that I wouldn't have considered them. Most people will have a lot more selection for lower competition keywords so these particular keywords from our test would not have been chosen. Another disappointing factor is that the one keyword that fell under the KC score significant, wasn't the article that performed the best for us.

But I would say that I've had success with using LTP in the past. With the Majestic metrics as well. It's really more about the age of that particular post as well. The older the post, the more weight that puts on it by Google.

The Worst Performer

Moz's keyword difficulty score performed the worst for us. 2/3 keywords showed that they were high competition and the 1 that wasn't considered low competition was in the higher range. Again, just like with LTP the best keyword choice from Moz wasn't the one that performed the best for us.

This test has led me to trust Moz metrics a lot less now. Which I think isn't surprising as many of the tools from Moz just haven't been working for a while. Namely the Mozbar chrome plugin which provides PA and DA data for web pages that you visit. It wasn't working until the recent update a few months ago.

Final Thoughts On These Keyword Difficulty Checkers

Some of you might be thinking that 3 articles isn't enough and you're right. However, these articles were chosen out of dozens, so we could have included those results as well. But it would just take up space to include the data, so we've chosen to compare the best performing articles for the keyword difficulty test.

To leave you guys with something concrete. It looks like Ahrefs keyword difficulty score is the most accurate and KWFinder is a close second.

If we left it at that, then Ahrefs would take the prize. But unfortunately, this is real life and pricing matters. Ahrefs lowest tiered plan is $990 per year whereas KWFinders lowest plan is $239 a year.

I would not suggest going for the lowest plan in KWFinder though. The number of related keywords provided on the lowest tier simply isn't enough to do proper keyword research. Meaning that when you enter in a seed keyword, you will only get 200 results vs. the 700 results from the next higher tier. I found this as a handicap in my previous review of KWFinder, but now that we've tested the KD scores with all these tools… KWFinder should be an even higher consideration given its price difference with Ahrefs and the accuracy of its keyword difficulty score.

Hopefully, this helps you guys understand more about what a keyword difficulty score is and how all the tools are vastly different in the ways they determine that score. At the end of the day, the keyword difficulty score is simply another filter for your keyword research. You'll want to do manual keyword research along with looking at metrics to ensure the best success for your site.

Leave a comment for us if you have any questions or what you've found from your own experiments!