SEO difficulty, usually called keyword difficulty, is a metric that estimates how hard it would be to rank on the first page of Google for a specific search term. Most SEO tools express it as a score from 0 to 100, where higher numbers mean tougher competition. It’s one of the first things content creators and website owners look at when deciding which keywords to target, but the number alone doesn’t tell the full story.
How the Score Is Calculated
Every SEO tool has its own formula, but they all lean heavily on one factor: backlinks. A backlink is a link from another website pointing to a page that ranks for the keyword you’re researching. The logic is straightforward. If the pages currently sitting on page one of Google have lots of links from other reputable sites, it will take significant effort to outrank them.
Semrush, one of the most widely used tools, bases its keyword difficulty percentage on two backlink-related signals. The first is the median number of referring domains linking to the top-ranking pages. More unique sites linking to those pages means a higher difficulty score. The second is the ratio of “follow” links to “nofollow” links. Follow links pass ranking power, so pages with a high proportion of them are harder to displace. Ahrefs, Moz, and other platforms use similar backlink-centric calculations, though the exact weighting differs from tool to tool.
What the Score Ranges Mean
Most tools break the 0-to-100 scale into broad tiers. Semrush, for example, labels scores of 0 to 14 as “very easy” and 15 to 29 as “easy.” Scores in the 30s and 40s are generally considered moderate, while anything above 60 or 70 is typically classified as hard or very hard. The labels vary slightly between platforms, but the principle is the same: lower scores suggest you can rank with less effort, higher scores suggest you’ll need strong content and a well-established site.
In practical terms, a keyword with a difficulty score under 30 often means the current top-ranking pages don’t have many backlinks, so a newer or smaller website has a realistic shot at reaching page one. A score above 70 usually means the results are dominated by major publications or well-known brands with deep link profiles, and breaking in will require a serious, sustained effort to build authority and earn links over time.
What Difficulty Scores Miss
The biggest limitation of keyword difficulty is that it’s almost entirely a backlink metric. That makes it a useful shorthand, but it ignores several factors that heavily influence whether you’ll actually rank.
Search intent. Google prioritizes pages that match what the searcher is really looking for. If someone searches “best running shoes,” Google serves product roundups and reviews, not e-commerce product pages. A page with perfect backlinks but the wrong format for the intent behind the query won’t rank well. Before chasing a keyword, look at the actual results and ask whether your content would fit naturally among them.
Topical authority. Google increasingly favors sites that cover a subject in depth. A health website with hundreds of well-linked articles about nutrition will have an easier time ranking for a new nutrition keyword than a general lifestyle blog, even if the lifestyle blog has more total backlinks. Difficulty scores don’t account for how relevant your site’s existing content is to the keyword.
Page experience. Fast loading speed, mobile-friendliness, and clean navigation all influence rankings. A technically polished page can outperform a slower, clunkier competitor even when the backlink profiles are similar. No difficulty tool measures this.
Content quality. Two pages targeting the same keyword with similar backlink counts can rank very differently based on how thoroughly and clearly they answer the searcher’s question. Depth, accuracy, and readability matter, and no score captures them.
How to Use Difficulty Scores Effectively
Think of keyword difficulty as a rough filter, not a verdict. It’s most useful in the early stages of keyword research when you’re sorting through hundreds of potential terms and need to quickly separate realistic opportunities from long shots.
If you run a newer website with few backlinks, filtering for keywords with difficulty scores below 30 helps you focus on terms where you have a genuine chance of ranking. As your site builds authority over months and years, you can gradually target higher-difficulty terms. Established sites with strong link profiles can afford to go after keywords in the 50-to-70 range and still expect results.
After the difficulty filter narrows your list, do the manual work. Search the keyword yourself and study the top results. Look at who ranks there: are they massive brands, or are some of them smaller sites with focused content? Check how many backlinks those pages have using a tool’s backlink analyzer, not just the difficulty score. Assess whether your content can genuinely be more useful, more current, or more complete than what already exists.
Why Scores Differ Between Tools
If you check the same keyword in Semrush, Ahrefs, and Moz, you’ll often get three different difficulty scores. This happens because each tool crawls the web independently, maintains its own index of backlinks, and weights its formula differently. None of them have access to Google’s actual ranking algorithm, so every score is an educated estimate.
This doesn’t make the scores useless, but it means you should pick one tool and use it consistently rather than comparing numbers across platforms. The relative ranking of keywords within a single tool is more reliable than the absolute number. If Tool A says Keyword X has a difficulty of 35 and Keyword Y has a difficulty of 62, the gap between them is meaningful even if another tool would assign different numbers to both.
Long-Tail Keywords and Lower Difficulty
One of the most practical applications of difficulty scores is finding long-tail keywords. These are longer, more specific search phrases that fewer websites are competing for. “Running shoes” might have a difficulty score above 80, but “best running shoes for flat feet under $100” could score below 20.
Long-tail keywords typically have lower search volume individually, but they tend to attract visitors who are closer to making a decision or taking action. A site that ranks for dozens of specific, low-difficulty long-tail terms can generate more useful traffic than one struggling to rank for a single high-difficulty head term. This is especially true for newer sites that haven’t yet built the backlink profile needed to compete on broader searches.
When building a keyword strategy, mixing a few ambitious higher-difficulty targets with a larger number of achievable long-tail terms gives you both short-term traffic and a foundation for long-term growth.