Keyword difficulty (KD) is a score from 0 to 100 that estimates how hard it is to reach page one of Google for a search term. Most tools base it mainly on the backlinks of the pages already ranking. A low score means a newer site has a fair chance. It is a rough guide, not a promise.
What is keyword difficulty?
Keyword difficulty is a number an SEO tool gives each search term. Higher means more competition. The point is to help you choose which questions to write about first, so you do not spend a month on a post that has no realistic path to page one.
The number is not a Google metric. Google does not publish one. Every tool invents its own, which is the first thing to remember when you read it.
How is keyword difficulty calculated?
Each vendor uses a different recipe, and the two biggest ones show how much the scores can differ.
- Ahrefs looks at the top 10 results and counts how many websites link to each. In its own words, KD is measured on a scale from 0 to 100, with 100 hardest, and it is an absolute metric built on backlink profiles. Their example: a score near 50 means the top pages have a couple of hundred backlinks, and above 90 means thousands.
- Semrush also studies the top 10, but uses six factors: referring domains, the ratio of follow to nofollow links, the authority of the ranking sites, the keyword's search volume, the SERP features it triggers, and whether the term is branded. Word count counts for less. Its ranges run from very easy (0 to 14) to very hard (85 to 100).
A score of 30 in one tool is not a score of 30 in the other. Pick one tool and compare keywords inside it, not across tools.
What is a good keyword difficulty for a small site?
There is no universal number, because the score describes the average site, not yours. Ahrefs says so directly: KD reflects how hard it is for the average website and does not account for your specific site's authority.
A practical way to use that for a new or small site:
- Start with terms in the easy bands of whichever tool you use (roughly the bottom third of the scale).
- Publish several posts there and see whether any reach page one in Search Console over the following weeks.
- If they do, move up one band. If they do not, the problem is probably the page or the site, not the score.
This turns the score into an experiment on your own domain instead of a rule from a vendor.
What does keyword difficulty miss?
Because the score leans on links, it can look easy when it is not, and hard when it is not. These are the gaps worth checking by hand.
- Intent. A keyword can score low and still be a poor fit if the results are all product pages and you have a guide. Read the results page first. Our post on search intent shows how.
- Result features. An answer box or AI summary can take the clicks even when you rank well. Semrush lists SERP features as a factor in the score, but a number cannot show you what the page looks like.
- Weak top results. Ahrefs notes that a high score does not show whether the top pages actually satisfy the reader, so it misses outdated or off-target pages that you could beat.
- Your own topic coverage. A site that already covers a subject in depth ranks more easily for its next question. That is topical authority, and no generic score sees it.
- Backlink quality. Ahrefs calls its own referring-domain estimate an estimation, because not all links carry equal weight.
A worked example: choosing between three keywords
Say you run a bookkeeping app and have three candidate posts. The numbers here are made up to show the thinking, not real data.
| Keyword | KD | What the results look like | Decision |
|---|---|---|---|
| what is accrual accounting | Low | Short definitions, mostly old | Write it first, with a worked example |
| best accounting software | High | Big review sites with many links | Skip for now |
| accrual vs cash accounting for freelancers | Low | Generic answers that ignore freelancers | Write it second |
Notice that the choice used three signals: the score, the age and quality of the results, and how specific the question is. The score alone would have only told you to avoid the second row.
How does keyword difficulty fit into keyword research?
It is a filter, applied after you know what your readers ask. First collect questions. Then drop the ones whose intent does not match what you can offer. Then use the score to order what is left. Our full process is in how to do SEO keyword research, and the next step, finding what rivals cover that you do not, is a content gap analysis.
Also check your own site before you commit. If you already have a page on the question, a second one risks keyword cannibalization. Update the old page instead.
Frequently Asked Questions
Is keyword difficulty the same in every SEO tool?
No. Each tool uses its own formula, so the same keyword can get different scores. Compare keywords inside one tool and ignore cross-tool comparisons.
Does a low keyword difficulty guarantee a page one ranking?
No. It estimates the competition, not your result. Page quality, search intent match and your site's own history still decide where you land.
Should I only target low difficulty keywords?
Start there if your site is new, since wins come faster. As you publish more on a subject and earn links, you can try harder terms in the same topic.
Does keyword difficulty account for AI answers?
The scores described by Ahrefs and Semrush are built on the ranking pages and, for Semrush, SERP features. Neither says it measures whether an AI answer will cite you, so check that separately.
What is the difference between keyword difficulty and search volume?
Volume is how many people search a term. Difficulty is how hard the results are to enter. A term can have high volume and high difficulty, or neither.