Keyword difficulty is the most-quoted number in SEO and the least examined.
People treat KD 30 as a fact. It is an estimate, produced by a proprietary model, that would give you a different answer if you opened a different tool.
It is still useful — we use it constantly, and it is how we sequence work. But you have to know what it is measuring, and more importantly what it cannot see. The wider process is in keyword research and our SEO guide.
What the score is built from
Details vary by tool, but the core input is consistent: the backlink profiles of the pages currently in the top ten. Referring domains, their authority, and how many of them each ranking page has.
Some tools layer on other signals — domain-level authority, SERP composition, click-through estimates — but backlinks do most of the work.
What the score cannot see
Four things, and any one of them can invert the judgement.
- Your own site. KD is calculated the same for a brand-new domain and for a fifteen-year-old authority site. It describes the competition, not the contest. KD 40 is trivial for one and impossible for the other.
- Content quality. If the top ten are thin, outdated pages with strong domains, the score reads as hard when the actual opportunity is wide open. Always look at the SERP.
- Intent match. A low KD term you cannot satisfy is not easy — it is unwinnable. See search intent.
- What the SERP is made of. A KD 30 keyword where a shopping carousel, a map pack and an AI Overview occupy the top of the page leaves very little organic real estate. See SERP features.
How to actually use it
Not as a gate. As a sorting tool.
- Sort by volume-to-difficulty ratio, not by either alone. A term at 1,000/mo and KD 20 is worth more than one at 6,600/mo and KD 68, because position is a multiplier on impressions — page one gets seen, page five does not.
- Set a ceiling honestly. A young site should generally stay under KD 40 for terms it intends to rank for this quarter. An established site can push higher.
- Open the SERP for anything you plan to write. Every time. The score is the filter; the SERP is the decision.
- Ignore it for entity coverage. Some pages exist to complete a topic rather than to rank alone. A KD 80 definitional page can still earn People Also Ask and AI Overview placements, and it strengthens the cluster around it.
- Re-check before you commit a URL. Check the acronym, the spelled-out form and the plus-modifier variant. The volume is often not where you assume.
The trap of chasing low difficulty
Filtering a list to KD under 20 and writing whatever survives feels efficient and usually is not.
Very low difficulty frequently means very low commercial value, or a query so specific that almost nobody searches it, or an intent your business cannot serve. You end up with a site that ranks well for things that never produce a customer.
Balance it against value. A hard term you can partly win is sometimes worth more than an easy one nobody needs answered.
Difficulty is not static
KD moves as the competition changes. A term that scored 35 last year can be 55 now because two strong sites published on it.
It also moves the other way. When a category's ranking pages go stale, difficulty falls even though the score has not caught up yet — which is exactly the window worth taking.
Where to go from here
Take your ten target keywords and calculate volume divided by difficulty for each. Re-sort the list. It will usually look quite different from your current priority order.
Then open the SERP for the top three and check that the ranking pages are actually strong, rather than merely well-linked. That gap is where the real opportunities are.
Frequently asked questions
What is keyword difficulty?
Keyword difficulty is a score, usually from 0 to 100, estimating how hard it would be to rank in the top organic results for a keyword. It is calculated mainly from the backlink profiles of the pages currently ranking — how many referring domains they have and how strong those domains are.
Why do tools give different keyword difficulty scores?
Because each tool maintains its own backlink index and its own proprietary formula. Semrush, Ahrefs and Moz are measuring similar things in different ways on different data, so their numbers are not comparable. Pick one tool and judge everything on its scale rather than converting between them.
What is a good keyword difficulty to target?
It depends entirely on your site, which is the score's main blind spot. A young domain should generally stay under about 40 for terms it wants to rank for this quarter. An established site can go higher. The score describes the competition, not the contest, so there is no universal number.
Should I only target low difficulty keywords?
No. Filtering to very low difficulty and writing whatever survives usually produces a site that ranks for things nobody needed answered. Low difficulty often correlates with low commercial value or an intent you cannot serve. Balance difficulty against what the traffic would actually be worth.
Does keyword difficulty account for my website's authority?
No, and this is the most important limitation. The score is calculated identically whether you are a brand-new domain or a long-established authority site. It measures how strong the incumbents are, not how likely you specifically are to displace them.
We sort by ratio, then check the SERP
Keyword plans that account for your domain, not just the competition's backlinks.