The appeal of an SEO score is obvious. One number, out of 100, that tells you how healthy your website is. Clean, simple, and almost entirely misleading.
The premise is simple: your site is scored out of 100, and a higher score means a healthier site, more traffic, and better results. In practice, it doesn't work that way. Sites with scores in the nineties can attract barely any traffic, while sites with far lower scores can perform extremely well. So what are SEO scores actually measuring, and why are they an unreliable guide to success?
How SEO Scores are Generated
SEO scores are produced by third-party tools like Semrush and Ahrefs. Each runs its own proprietary scoring formula, none of which are provided by, endorsed by, or visible to Google. They are, at best, each tool's attempt to summarise your website's health into a single number.
The problem is that Google's algorithm is far too complex for any score to capture. It weighs an array of ranking factors differently depending on the query, the user, and the context.
Think of how a doctor assesses your health. They examine dozens of markers, weigh them against one another, and form a judgement. The outcome is a diagnosis and a set of recommendations, not a number. SEO should be no different.
Why You Shouldn’t Take SEO Scores at Face Value
Take Semrush's Site Health score as an example. It flags quantifiable signals: 404 errors, low word counts, missing page titles. The logic seems reasonable until you realise the tool has no way of knowing whether any of those flags are actually problems.
A page with a low word count isn't automatically a poor page. A calculator or file converter might not need hundreds of words to satisfy search intent. But because the tool counts words rather than judging whether those words were needed, it penalises pages that are, by every practical measure, doing exactly what they should. This is the real danger of optimising for SEO scores, that is, you risk chasing an arbitrary metric instead of the things that actually matter.
Why SEO Scores Are So Widely Used
If SEO scores are unreliable, why do platforms like Semrush and Ahrefs include them at all?
Because they are easy to present. A number out of 100 requires no explanation. A client, a marketing director, or a board can look at it and feel informed, regardless of whether the number reflects anything meaningful about how the site is actually performing.
The tools are responding to a real demand. Stakeholders want simple answers, and a score delivers that. The problem is that when SEO scores are used to communicate performance, they start to shape priorities. Teams optimise for the number because the number is what gets reported. Not because it reflects what matters.
The Right Way to Approach SEO Scores
None of this is an attack on SEO tools and the value they provide. Used well, they help to surface genuine issues worth addressing. Rather, the mistake is treating a diagnostic instrument as a report card.
Some argue the solution is to treat SEO scores as directional rather than absolute, or to apply custom weights to each factor. That has some merit, but in practice, these scores can be directionally wrong, and a weighted score still doesn't tell you much beyond what an experienced SEO already knows from looking at the site.
The more productive question is never "how do we improve the score?" It's "how do we improve the site?".
What to Measure Instead of SEO Scores
The metrics worth tracking are the ones tied to real business outcomes.
Organic traffic shows whether more people are finding your site through search. Keyword rankings tell you where you stand for the terms that matter to your business. Organic conversions and revenue show how the above actually translate into business outcomes.
None of these fit neatly into a single score, and that's precisely the point. SEO performance is multidimensional. The goal is not to find a better number to chase, but to build a clearer picture of what is working, what isn't, and what to do next.