Glossary
What is keyword difficulty?
Keyword difficulty (KD) is an SEO tool's estimate, usually 0 to 100, of how hard it would be to rank on the first page for a search. Most tools base it largely on the backlink strength of the pages currently ranking. Each tool calculates it differently, so scores aren't comparable across tools.
How tools calculate it
Ahrefs' KD is based on how many referring domains the top-ranking pages have. Semrush's combines several factors including authority and search results features. Moz uses its own model. The same keyword can be "easy" in one tool and "hard" in another.
Blind spots
- Ignores whether ranking pages match the intent well.
- Ignores how outdated or thin ranking content is.
- Ignores your own topical authority.
- Doesn't capture AI Overviews taking clicks.
Judging it yourself
Look at the top results: are there big brands only, or forum posts and small blogs? Are pages current and thorough? Do any directly answer the question? A high KD with weak, outdated pages can be a real opportunity.
Example
"Dofollow directories" shows a medium KD. The top results are old lists with dead sites. A current, checked list with data ranks despite the score.
FAQ
What is a good keyword difficulty for a new site?
Low scores in your tool, but always check the actual results.
Why do tools disagree on KD?
Different formulas and link indexes.
Does Google have a keyword difficulty score?
No. KD is a third-party estimate.
Should I avoid high-difficulty keywords?
Not entirely; target them with your best pages over time, and win long-tail variants first.