What Is Keyword Difficulty? How to Read and Use the Score
Keyword difficulty is a score, on a 0 to 100 scale in the major tools, that estimates how hard it would be to rank on the first page of Google for a search term. It is not a Google metric. Google publishes no difficulty score, and every number you see comes from a third-party tool’s own model, built from that tool’s own data. Read it as one vendor’s estimate of the competition, useful for comparing keywords inside the same tool and weak as a forecast for your own site.
What the Score Measures
The tools start from the same raw material: the pages already ranking for a keyword and the links pointing to them. They differ in what else they add.
Ahrefs states in its Help Center that its Keyword Difficulty “is based on the number of referring domains (RDs) the Top 10 ranking pages (organic search results only) for a given keyword have,” and adds: “KD does not take into consideration any ‘on-page SEO’ factors.”
Semrush’s knowledge base lists a broader set: “the median number of referring domains pointing to the URLs that are ranking, the median ratio of dofollow/nofollow links pointing to these, the median authority score of the domains that are ranking,” and qualities of the results page itself.
Because each vendor defines the score differently, a number only means something next to other numbers from the same tool.
Why Two Tools Disagree
| Cause | Effect |
|---|---|
| Separate link indexes | Each tool crawls the web on its own, so the referring-domain counts behind the score differ |
| Separate formulas | Ahrefs counts referring domains to the top 10; Semrush also weighs link ratios, domain authority, and the results page |
| Separate authority scales | Domain Rating, Domain Authority, and Authority Score are different vendor metrics, not one measure under three names |
None of these makes one tool right and another wrong. They are different estimates built from different data.
How Specificity Changes the Picture
For example, imagine three versions of one topic: “project management software,” “project management software for architecture firms,” and “free project management software for small creative agencies.” The broad term draws pages from large software review sites and major brands; the narrower phrases may bring up a different set of pages. A score such as Ahrefs’ KD is built from the links of the top ten ranking pages, so narrower wording lowers it only if the pages ranking for it have fewer links, and a specific phrase can score as high as a broad one. The score for any real phrase comes only from looking it up in a tool. The example shows what to compare, not the numbers.
What the Score Leaves Out
A standard difficulty score is the same for every site that looks it up. Because it is built from links and, in some tools, from the results page, it does not see:
- whether your page answers the query better than the pages ranking now
- your own site’s links and topical history
- whether your page type matches what ranks (a product page among how-to guides, for instance)
- page experience, internal linking, and technical health
- how stable the current top results have been
Some tools add a separate, site-specific estimate. Semrush’s Personal Keyword Difficulty, for example, “answers how difficult it will be for the specified domain to reach the top 10 of the SERP for the specified keyword.” Read it as a different metric from the standard score.
It also does not tell you how many clicks the first position will get. When an AI Overview or another feature sits above the organic results, a low-difficulty keyword can still send far fewer visits than its search volume alone would suggest.
Using the Score in a Decision
- Read difficulty next to search volume and business value. A low score on a term nobody searches, or on a term unrelated to what you offer, is not a priority.
- Open the results page. Look at who ranks, what format dominates, and whether your site has a realistic basis to compete with those specific pages.
- Compare the competing pages with yours directly: intent, content, and the links each has earned. A difficulty score and a site-strength score such as Domain Rating are not on one scale, so matching the two numbers says little.
- Compare keywords in broad bands. A few points of difference on a 100-point estimate is too small to separate two keywords on its own.
Questions About Keyword Difficulty
Is keyword difficulty a Google ranking factor?
No. It is a vendor metric that Google does not publish, and Google’s guidance on third-party SEO tools notes that such tools cannot see Google’s internal ranking data.
Should I avoid every high-difficulty keyword?
Not by the score alone. A high score reflects strong link competition, and a site with established authority on the subject, or a page that answers the query clearly better than the current results, can still compete.