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Why it matters for founders and small teams
Keyword difficulty is how a small team avoids spending three months on a topic it was never going to win. Used well, it points a young site at the questions where today’s ranking pages are beatable; used badly, it steers you away from the specific, low-competition questions that AI engines increasingly search on your buyer’s behalf.
How is keyword difficulty calculated?#
Keyword difficulty is calculated mostly from the backlink strength of the pages in Google’s top 10 today: Ahrefs counts how many sites link to each of them, while Semrush blends referring domains, link types, authority scores and SERP features — so each tool gives the same keyword a different score.
| Score | Main inputs | Output |
|---|---|---|
| Ahrefs KD | How many websites link to each of the top 10 ranking pages | 0–100, read as a rough link budget |
| Semrush KD% | Median referring domains to the top 10, median dofollow-to-nofollow ratio, median Authority Score of the ranking domains, and SERP features | 0–100, in six bands from very easy to very hard |
| Semrush Personal KD | Adds your own domain’s topical relevance and metrics against the competitors on the results page | A score for your site specifically |
Ahrefs frames its score as roughly how many referring domains a page needs to reach the first page. At the bottom of the scale the top pages have few backlinks; around KD 50 they have a couple of hundred; above 90, thousands. None of these tools reads Google’s ranking systems. Keyword difficulty is a model of the current results page built largely from backlink data — not a Google metric.
What is a good keyword difficulty score?#
A good keyword difficulty score is one at or below what your site already ranks for. Semrush labels 0–14 very easy and 30–49 possible, but a young site with few backlinks should start far lower than an established one, because the score ignores who is trying.
| Semrush KD% | Band | What Semrush says it takes |
|---|---|---|
| 0–14 | Very easy | The best chance to rank new pages quickly, with the least effort |
| 15–29 | Easy | Achievable even for a new domain, with quality content focused on intent |
| 30–49 | Possible | Quality, well-structured content properly optimized for the keyword |
| 50–69 | Difficult | Some quality backlinks plus well-structured, optimized content |
| 70–84 | Hard | Better-quality backlinks supporting well-optimized, unique content |
| 85–100 | Very hard | High-quality content and link building, plus on-page SEO and promotion |
The bands describe an average site. Ahrefs is explicit that its score doesn’t account for your own site’s authority, content quality, search intent match or freshness. The practical fix is to calibrate the score against yourself — the worked example below shows how.
Worked example
The KD Ceiling Test
A way to turn a generic difficulty score into a personal one: find the hardest keywords your site already ranks for and treat that as your ceiling. The inputs are illustrative, for a fictional project management tool called Plannora, and the 10-point stretch is a rule of thumb, not a vendor standard.
- 1
Pull the queries you already rank for
Search Console, last three months: non-branded queries with an average position of 10 or better.
38 queries
- 2
Find your ceiling
Run all 38 through one keyword tool. The hardest queries Plannora holds in the top 10 score KD 21, 22 and 24.
KD 24
- 3
Set the target band
The ceiling plus about 10 points of stretch.
KD ≤ 34
- 4
Filter the candidate list
Of 50 candidate buyer questions from research, 19 fall inside the band.
19 of 50
- =
Winnable topics
Drop the questions whose top results are a different page type — tools, product pages, forum threads — from the article Plannora would write.
12 topics
The result: Twelve topics Plannora can realistically win now, instead of fifty ranked by a score built for an average site. Recalculate the ceiling each quarter: as the site earns links, the ceiling rises and the next band opens. Semrush’s Personal Keyword Difficulty automates a version of the same idea inside its tool.
Free to use and adapt. If you cite it, link to rankbox.xyz/glossary/keyword-difficulty.
Does keyword difficulty matter for AI search?#
Keyword difficulty matters less for AI search than for Google rankings, because AI engines rewrite each prompt into narrower sub-queries and often cite pages outside the top 10 — so a high-difficulty head term can still be reached through the easier questions around it.
37.9%
of pages cited in Google AI Overviews rank in the top 10 for the query the user typed
~8%
of ChatGPT's citations rank in Google's or Bing's top 10 for the original prompt
0.218
correlation between backlinks and brand visibility in AI Overviews, against 0.664 for branded web mentions
Keyword difficulty measures the links behind one results page; AI engines fan the question out and pick passages from many. That makes KD a weaker guide to who gets cited, and it means long-tail keywords with low volume and low difficulty often match the sub-queries an engine writes. Claude adds a twist: it searches Brave, not Google, so a Google-based score says little about Claude at all.
Common mistakes with keyword difficulty#
The most common keyword difficulty mistakes are comparing scores across tools, treating KD as a Google metric, ignoring the results page and skipping zero-volume questions — each picks topics by something the number was never designed to measure.
Myth
KD is how Google rates the keyword.
Reality
Google doesn’t publish any difficulty score. KD is a vendor’s model, built mostly from backlink data about the pages ranking today.
Myth
A low KD means I'll rank.
Reality
Ahrefs notes KD ignores content quality, intent and freshness. If the top results are a different page type from yours — tools, product pages, forum threads — the score won’t save you. Read the SERP first.
Myth
Zero volume means zero value.
Reality
Specific buyer questions often show little or no volume in keyword tools, yet they can be exactly what buyers ask AI assistants. Judge them by intent.
Myth
A high-KD topic is off-limits.
Reality
It’s off-limits as a head term for now. Its sub-questions usually aren’t, and a topic cluster built from them earns the links and relevance to compete later.
Related terms#
- Content & relevanceLong-tail keywordsSpecific search phrases that each draw few searches but together make up the vast majority of distinct queries, and because they signal precise intent they are the closest classic-SEO match to the conversational prompts people type into AI.Read the entry
- Content & relevanceSearch intentThe goal behind a query — to learn something, reach a specific site, compare options or buy — and matching it decides which kind of page, from a guide to a product page to a comparison, search engines and AI answers treat as relevant.Read the entry
- Authority & off-siteBacklinksA link from one website to another, which search engines treat as a vote of confidence that passes authority to the page it points to — and the relevance and quality of the linking site matter far more than the number of links.Read the entry
- DAAuthority & off-siteDomain authorityA third-party score from 1 to 100, created by Moz, that predicts how well a website is likely to rank based mainly on its backlinks; Google does not use it, and comparable metrics include Ahrefs’ Domain Rating and Semrush’s Authority Score.Read the entry
- Authority & off-siteTopical authorityThe degree to which search engines and AI systems treat a site as a reliable source on a whole subject, earned by covering that subject in depth and being referenced for it elsewhere, rather than by ranking for any one keyword.Read the entry
- MeasurementSERPThe page a search engine returns for a query, which today mixes classic blue links with AI Overviews, ads, featured snippets, videos, forum threads and other features competing for the same attention.Read the entry
Go deeper
Sources
- 1.Keyword difficulty: how to estimate your chances to rankAhrefs · ahrefs.com ↗
- 2.Keyword Difficulty scoreSemrush Knowledge Base · semrush.com ↗
- 3.How is Personal Keyword Difficulty calculated?Semrush Knowledge Base · semrush.com ↗
- 4.How many AI Overview citations rank in the top 10?Ahrefs · ahrefs.com ↗
- 5.AI search overlap with Google and BingAhrefs · ahrefs.com ↗
- 6.An analysis of AI Overview brand visibility factors (75K brands studied)Ahrefs · ahrefs.com ↗
