Keyword Difficulty

Why do two tools give different difficulty scores?

Because they are different models measuring different inputs against different link indexes. No search engine publishes a difficulty figure, so every score is a vendor’s construction, and a score of 40 in one product is not comparable with a 40 in another. Comparing them across tools is the most common way the number gets misused.

Within one tool the score is genuinely useful, because it is consistent: it ranks keywords against each other on one methodology, which is the job it was built for. The other limitation is what the score cannot see. Difficulty models the pages currently ranking, so it describes the competition that exists rather than the competition a good page would face, and it says nothing at all about whether the intent behind the query is one you can serve.

It is also blind to the thing that decides most outcomes on a small site, which is whether you have anything to say. A difficulty score of 8 on a subject you know nothing about is harder in practice than a 45 on the thing you do every day.

What can keyword difficulty not tell you about AI answers?

Almost everything, because it models the wrong competition. Difficulty scores are built largely from backlinks, and in Ahrefs’ study of 75,000 brands backlinks were among the weakest correlates of AI visibility at 0.218, against 0.664 for branded web mentions. A keyword that is hard to rank for is not necessarily hard to be cited on.

Moz’s finding that 88% of AI Mode citations do not match the organic top 10 points the same way from the other side. The page cited was often not competing on that keyword at all, so its difficulty was never the relevant number.

How should the score change what you do?

Use it to sequence work within search, and set it aside when choosing what to answer for assistants. The questions worth answering for an answer engine are chosen by whether you have something specific to say, not by how many links the incumbents have.

The recommendation, which could be wrong for a site with no authority at all: write the page you would be uniquely good at even when the difficulty score is discouraging, and skip the easy keyword you have nothing to add on. The second one ranks and is never cited.

Related terms

• Search VolumeSearch volume is an estimate of how often a keyword is searched in a given period, usually per month and per country.
• Domain Rating (DR)Domain Rating is Ahrefs’ score, from 0 to 100, for the strength of a website’s backlink profile relative to every other site in its index.
• Long-Tail KeywordA long-tail keyword is a longer, more specific search phrase with lower individual volume than a head term.
• Information GainInformation gain is how much new information a document adds beyond what a reader has already seen elsewhere.