What Is Keyword Difficulty?
Keyword difficulty (KD) is a 0–100 score estimating how hard it would be to rank in the top search results for a given keyword, based mainly on the authority and backlink strength of the pages already ranking there.
How it’s actually calculated
There’s no single, standardized formula, every major tool weighs it slightly differently, but most are built from the same core inputs:
- Referring domains: how many unique websites link to the pages currently ranking on page one
- Domain and page authority: the overall strength of the ranking sites, not just the linked page
- Content depth: how comprehensively the top-ranking pages already cover the topic
- SERP features and paid competition: heavy ad presence or dense SERP features usually signal a more competitive, higher-value term
Ahrefs, for instance, largely bases its KD score on the number of referring domains pointing at the top 10 results. Semrush blends SERP analysis with keyword-level and locality data. Moz weighs Page Authority and Domain Authority together and adjusts for projected click-through rate. Same 0–100 scale, three different scores for the exact same keyword, which is why comparing KD numbers across tools is unreliable. Only compare scores within the same tool.
How the three major tools score the same keyword
Because there’s no industry standard, the same keyword can carry noticeably different KD scores depending on which tool pulled it. For illustration, a broad commercial term like “project management software” might come back roughly like this:
| Tool | Primary basis for the score | Illustrative score |
|---|---|---|
| Ahrefs | Referring domains to the top 10 results | ~62 |
| Semrush | SERP analysis blended with keyword and locality data | ~71 |
| Moz | Page Authority and Domain Authority, adjusted for projected CTR | ~58 |
None of these scores are “wrong” relative to each other, they’re measuring slightly different things. This is exactly why tracking KD trend over time within a single tool is far more useful than comparing an absolute number pulled from two different platforms.
Example
A broad, category-defining keyword like “insurance” might carry a difficulty score around 85, dominated by national brands with thousands of referring domains. A specific, niche term like “pet insurance for senior rabbits” might score closer to 10 to 15, since only a handful of thin, poorly optimized pages compete for it, and a smaller site has a realistic shot at ranking.
Where teams misuse it
The most common mistake is treating KD as an absolute probability of ranking rather than a relative measure of competition. A “40” isn’t inherently safe and a “70” isn’t inherently hopeless, it depends entirely on your own site’s current authority. A well-established, high-authority domain can realistically compete for keywords a brand-new site should avoid entirely, and a new site chasing a “medium difficulty” term can still stall out for months with nothing to show for it.
The second mistake is optimizing for difficulty alone. Difficulty only means something next to search volume and search intent, a low-difficulty keyword nobody searches for isn’t a win, it’s wasted content production.
How to actually use it
Rather than reading the score in isolation, open the top 10 ranking pages directly and check what the number is actually describing: how many strong referring domains they carry, how comprehensively they cover the topic, and whether their on-page optimization has obvious gaps. A “high difficulty” score sitting on top of thin, dated content is a very different opportunity than the same score sitting on top of ten genuinely excellent, deeply-linked pages.
In practice, this means weighing three things together instead of one: difficulty against your site’s current authority, search volume against how closely the term matches your actual audience, and both against how well you can realistically outdo what’s already ranking. This is the same framework covered in keyword research for beginners, difficulty is one input into that decision, never the whole decision.
Why it matters
Keyword difficulty helps teams set realistic expectations and prioritize keywords where their site actually has a reasonable chance to rank, rather than burning months of content production competing head-on with far larger, more established domains on the hardest terms. Used alongside long-tail keyword targeting and real keyword research, it’s one of the fastest ways to find keywords worth the effort instead of guessing.
Frequently asked questions
What counts as a “good” keyword difficulty score for a new website?
There’s no universal number, it depends on your domain’s current authority. As a rough starting point, brand-new sites with little backlink history typically have the most realistic shot at keywords scoring under 20-30 in most tools, while established sites with a strong backlink profile can reasonably compete further up the scale.
Does a low keyword difficulty score guarantee a fast ranking?
No. KD only measures the current competition on page one, it says nothing about whether your own content is actually strong enough, whether Google trusts your site yet, or how long ranking typically takes for that topic. Low difficulty shortens the odds, it doesn’t guarantee the outcome.
Should I ignore high-difficulty keywords entirely?
Not necessarily. High-difficulty terms are often worth targeting with a long-term content and link building strategy once your site has enough authority, they’re just poor first targets for a brand-new domain still building trust.