Introduction to AI Search and Backlinks
Historically, backlinks have been one of the most reliable currencies of visibility in search results. However, with the rise of AI search models, the rules of organic visibility and competition for share of voice in LLM results are changing. The question is, do backlinks still earn visibility in AI-based modalities of search, and if so, which ones?
Understanding the Analysis
Together with Semrush, an analysis of 1,000 domains and their AI mentions against core backlink metrics was conducted. The data surfaced four clear takeaways:
- Backlink-earned authority helps, but it’s not everything.
- Link quality outweighs volume.
- Most surprisingly, nofollow links pull real weight.
- Image links can move the needle on authority.
Methodology
For this analysis, relationships between AI mentions for 1,000 randomly selected web domains were examined. All data is from the Semrush AI SEO Toolkit, Semrush’s AI visibility & search analytics platform. The number of mentions across various platforms, including ChatGPT, ChatGPT with Search activated, Gemini, Google’s AI Overviews, and Perplexity, was measured against backlink metrics such as Total backlinks, Unique linking domains, Follow links, Nofollow links, Authority Score, Text links, and Image links.
Correlation Coefficients
Two different ways of measuring correlation across the data were used: a Pearson correlation and a Spearman correlation. Both are correlation coefficients – numbers between -1 and +1 that measure how strongly two different variables are related. The closer the coefficient is to +1 or -1, the more likely and stronger the correlation.
Findings
The first signal examined was the strength of the relationship between the number of backlinks a site gets versus its AI Share of Voice. The data showed that Authority Score has a moderate link to Share of Voice (SoV): Pearson ~0.23, Spearman ~0.36. Higher authority means higher SoV, but the gains are uneven. There’s a threshold you need to cross. Also, the number of unique linking domains matters more than the total number of backlinks.
Authority Score and Mentions
Across all models, the strongest relationship occurred between Authority Score and the number of mentions. The data showed that Authority Score (0.65 Pearson, 0.57 Spearman) and the number of mentions are strongly related. The relationship is non-linear, meaning the biggest gains come when you hit the upper boundaries of authority, or Ascore in this case.
Nofollow Links
Perhaps the most significant finding from this analysis is that it doesn’t matter much if the links are set to nofollow or not. Confirmation of the value of nofollow links is so important because these types of links tend to be easier to build than follow links. The data showed that follow links and nofollow links have similar correlations with mentions: Follow links → Mentions: Pearson 0.334, Spearman 0.504, and Nofollow links → Mentions: Pearson 0.340, Spearman 0.509.
Image Links
Beyond text-based backlinks, image-based backlinks were also tested. The data showed that image links can have a stronger relationship to mentions than text-based links. Images vs mentions: Pearson 0.415, Spearman 0.538, and Text links vs mentions: Pearson 0.334, Spearman 0.472. Image links really start to pay off once you already have some authority.
Conclusion
In conclusion, backlinks still earn visibility in AI-based modalities of search, but the rules have changed. Link quality outweighs volume, nofollow links pull real weight, and image links can move the needle on authority. The data showed that Authority Score is a strong indicator of AI mentions, and the relationship between backlinks and AI mentions is non-linear. Understanding these findings can help marketers influence visibility in AI search results and make informed decisions about their SEO strategies.