86% of Top Mentioned Sources Are Not Shared Across ChatGPT, Perplexity, and AI Overviews

Good content is good content, and top websites are top websites. These things don’t change. However, biases in the training data and partnerships can change which sources are mentioned by different AI Assistants.

AI Assistants may also work slightly differently. By default, they don’t have any notion of websites and can make up sources. Looking at you ChatGPT.

Some systems are augmented with search, where they retrieve documents first and they’re less likely to hallucinate results. Some bias towards partners that they paid to license the data.

Contents

Only 14% of the top 50 mentioned sources were shared across ChatGPT, Perplexity, and Google AI
Why are they different?
How they bias

Looking at the top 50 most mentioned websites in Ahrefs Brand Radar for AI Overviews, ChatGPT, and Perplexity, only 7 websites are in the top 50 results for all of them.

This is across ~76.7M AI Overviews, 957k ChatGPT prompts, and 953.5k Perplexity prompts for the month of June 2025.

Sidenote

Brand Radar isn’t just another LLM visibility monitor, we track a large amount of queries across all of these systems and you can query for any product, service, or brand and compare vs competitors. It’s more like Site Explorer than it is Rank Tracker.

Here's what Brand Radar looks like.

Here’s the overlap:

And here’s what is included in each:

Systems work in slightly different ways. For example:

Platform	How it chooses citations
Perplexity	Real-time web search → ranks → quotes → cites best matching source
ChatGPT (with browsing)	Search → filters for trusted/licensed domains → cites
ChatGPT (default)	No citations unless prebuilt → may hallucinate
Google AI Overviews	From search index → curated citation list
Bing Copilot	Uses Bing search → highlights snippets → includes citations

Various biases and different methodologies mean that even for the same queries, these systems may cite completely different websites.

There are going to be additional biases introduced based on the types of sites blocking AI bots and those that render JavaScript like Google, vs those that don’t, which is most of the rest of them.

Google AI Overviews lean towards the same top sites we’re used to seeing in search results. There’s a heavy emphasis on authoritative websites for health, finance, encyclopedic knowledge, social media, as well as a bias for Google-owned properties. Notably missing are media sites, non-Google entertainment sites, and ecommerce sites.

ChatGPT leans more on publishers and non-Google media, especially for news, entertainment, and sports. They have licensing deals and partnerships with many of the cited websites. ChatGPT doesn’t have much around health or medicine.

Perplexity pulls from a broader international corpus. There are many local and regional brands that weren’t in the top 50 for the other AI assistants. Perplexity doesn’t have social websites or traditional Western media.