Keyword difficulty
Also called KD, competition score
A normalised score estimating how hard it would be to rank on the first page for a keyword, derived from the strength of the pages currently ranking for it. Scores are provider-specific and are not comparable between tools.
Difficulty is a model, not a measurement. Every provider builds it from the same raw ingredients — the link profiles, authority and relevance of the pages already ranking — and every provider weights them differently.
Two consequences follow.
Scores are not portable. A 42 in one tool is not a 42 in another. Comparing difficulty across tools is comparing two models, not two measurements. Pick one source and stay with it.
The score is a prior, not a verdict. A high difficulty on a query where every ranking page is a marketplace listing and you are a specialist is a different situation from a high difficulty on a query dominated by peers. The number cannot see that. The SERP can, which is why difficulty is worth reading next to the actual results rather than instead of them.
Used well, difficulty is a sorting tool: it tells you which of two hundred candidate keywords in a research run to look at closely first. Used badly, it is a reason to skip a term you could have won.
Last reviewed . Also served as markdown at /glossary/keyword-difficulty.md.