Google reached 93.7% of ChatGPT’s website visitors in September 2026, according to Similarweb’s audience figures. Looking at the overlap from the other direction, 14.1% of Google’s visitors also visited ChatGPT.
The comparison covers Google.com and ChatGPT.com worldwide. Similarweb clarified in a reply that it counts unique monthly visitors who visited both sites, rather than raw sessions. It therefore concerns shared web audiences, not combined use across websites and apps.
The figures were highlighted by SEO consultant Gagan Ghotra. The published data contains no purchase tracking or information about which service people visited first.
The percentages start with different audiences
Similarweb uses each website’s own visitor base as the starting point. A group that represents a small portion of Google’s audience can account for most of ChatGPT’s audience because the two totals differ.
Marketers treating Google and ChatGPT visitors as entirely separate groups would count many of the same people twice.
Someone could move most of their searches to ChatGPT and still appear in the overlap after visiting Google once that month. The shared visitor count would stay the same even as their frequency of Google use fell.
Measuring that shift would require activity data, such as how many searches those visitors made on each service over comparable periods. September’s visitor percentages leave that question open, even with a large overlap.
When ChatGPT referrals appear as Direct traffic because source information is missing, site analytics can understate the service’s contribution. Comparing total visits to the affected landing pages with their source breakdown can help identify an attribution change before treating it as lost traffic.
Source: Similarweb
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