SEMrush vs Ahrefs for Keyword Research in 2026: Which Has Better Data?

Both SEMrush and Ahrefs are used by professional SEO teams for keyword research. The question of which has better data is worth examining with specific test cases rather than general claims.

Testing methodology

We ran keyword research on 50 terms across three categories: high-volume commercial keywords, medium-volume informational keywords, and low-volume long-tail keywords. We compared the data against confirmed Google Search Console data for terms where we had reliable ground truth. We looked at search volume accuracy, keyword difficulty score accuracy, and the quality of keyword suggestions.

Search volume accuracy

For high-volume keywords above 10,000 monthly searches, both tools were within 20% of actual Search Console data, which is acceptable given the estimation methodology. For medium-volume keywords between 500 and 5,000 searches per month, Ahrefs was closer to Search Console data in our testing. For low-volume keywords under 500 searches, both tools are unreliable and the estimates vary widely. This is a known limitation of both platforms.

Keyword difficulty scores

Keyword difficulty scores between the two platforms are not directly comparable because they use different methodologies. Ahrefs KD is based on the number of backlinks needed to rank in the top 10. SEMrush KD is based on a proprietary formula involving multiple factors. In our testing, Ahrefs KD scores more accurately predicted ranking difficulty for informational content. SEMrush KD was slightly more accurate for commercial terms.

Keyword suggestions quality

Both tools generate large numbers of related keyword suggestions. SEMrush tends to surface more semantically related terms. Ahrefs Parent Topic feature is more useful for understanding the broader keyword landscape around a topic. For building out a content cluster, Ahrefs Parent Topic is a genuine differentiator.

The verdict

Ahrefs has a marginal advantage in keyword research data quality, particularly the Parent Topic feature and accuracy for informational content. SEMrush is slightly better for commercial keyword research and has a better user interface for keyword research tasks. The difference is not large enough to drive the purchasing decision on its own. Both are excellent tools and other factors like backlink analysis and site audit quality should also inform your choice.