Ask three reputable trackers what ChatGPT market share is right now and you'll get three different answers, none of which round to the same number. Sensor Tower says 46.4%. First Page Sage says 52.7%. Similarweb says roughly 53%. That's a six-point spread on the single most-cited stat in AI search right now, from three firms with real methodology and real data, published within weeks of each other. Nobody's lying. They're measuring different things.
Three trackers, three numbers, one direction
Start with the headline that made the rounds in mid-June. TechCrunch reported on June 16, 2026 that Sensor Tower's "State of AI Report 2026" measured ChatGPT chatbot usage share at 46.4% as of May 2026, with Gemini at 27.7% and Claude at 10.3%. Sensor Tower also put raw monthly active users at 1.1 billion for ChatGPT, 662 million for Gemini, and 245 million for Claude. The headline framing was specific: this was the first time Sensor Tower's tracking had ever shown ChatGPT under 50% share.
Six weeks later, a different picture landed from a different methodology. Similarweb's GEO stats page, updated July 29, 2026, tracks a full year, June 2025 through May 2026, using web-traffic share rather than app usage. Over that window, ChatGPT's share fell from roughly 76% to roughly 53%. Gemini climbed from under 9% to somewhere around 27-28%. Claude went from roughly 2% to roughly 9%. Same direction as Sensor Tower's numbers. A starting point 30 points higher and an ending point nearly 7 points higher for ChatGPT.
Then there's First Page Sage, whose report is updated on a rolling basis and most recently refreshed July 20, 2026. Their tracking window runs January through July 2026: ChatGPT fell from 67.1% to 52.7%. Gemini sits at 27.7%, matching Sensor Tower's figure almost exactly. Claude sits at 10.3%, also matching Sensor Tower. Grok comes in at 2.8%, Perplexity at 2.0%.
Line all three up and you get a genuinely useful table, not because it resolves the disagreement, but because it shows exactly where the disagreement lives.
| TRACKER | DATE / WINDOW | CHATGPT | GEMINI | CLAUDE | NOTES |
|---|---|---|---|---|---|
| Sensor Tower (via TechCrunch) | As of May 2026 | 46.4% | 27.7% | 10.3% | Chatbot usage share; first time ChatGPT measured under 50% in this tracker |
| Similarweb | Jun 2025 – May 2026 | ~76% → ~53% | <9% → ~27-28% | ~2% → ~9% | Web-traffic share, full-year trend, updated Jul 29, 2026 |
| First Page Sage | Jan 2026 – Jul 2026 | 67.1% → 52.7% | 27.7% | 10.3% | Blended tracking metric, updated Jul 20, 2026; also tracks Grok 2.8%, Perplexity 2.0% |
Notice what actually lines up and what doesn't. Sensor Tower and First Page Sage agree almost exactly on Gemini (27.7% both) and Claude (10.3% both), despite using different methodologies and different windows. But their ChatGPT numbers sit 6.3 points apart, 46.4% versus 52.7%, for roughly the same moment in time. Similarweb's endpoint, ~53%, lands close to First Page Sage's 52.7% but its starting point, ~76%, is nowhere near First Page Sage's January figure of 67.1%, because it's measuring a different eleven months and a different signal entirely.
Why the numbers don't match
This isn't sloppy research from any of the three. It's three different instruments pointed at three different slices of the same market, and each one is internally consistent, just not comparable to the others without a lot of caveats nobody puts in the headline.
ChatGPT's reported share, same rough moment, three trackers — the spread is the story
Sensor Tower is measuring app-level chatbot usage share, built off its mobile and app-intelligence panel, and reporting raw monthly active users alongside the percentage. Similarweb is measuring web-traffic share, built off its browser and DNS-level panel, which captures desktop and browser usage that an app-focused panel undercounts and vice versa. First Page Sage doesn't fully disclose its blend but reports a single tracking metric updated on a rolling window, which is why its number sits between the other two. None of these panels sample the same population of users, none of them weight mobile versus desktop the same way, and none of them define "usage" identically. A 6-point gap between two firms measuring roughly the same month is not a scandal. It's what you'd expect from three different sampling methodologies pointed at a market that's genuinely moving fast underneath all of them.
What all three actually agree on
Strip out the decimal points and the three reports tell the same story in three different accents. ChatGPT went from dominant to merely largest. All three trackers now put it in the low-to-mid 50s or below, a category shift from where it sat a year ago in the high 60s to high 70s depending on which panel you trust. Gemini is the clearest winner of the last twelve months, more than tripling its share on two of the three trackers and roughly matching Sensor Tower and First Page Sage's identical 27.7% figure. Claude went from a rounding error, roughly 2% on Similarweb's mid-2025 baseline, to a real double-digit player at 9-10.3% across all three sources.
This is the pattern we flagged in our earlier look at the AI search leaderboard: the engine rankings move fast enough, and get reported inconsistently enough, that nobody should be memorizing a specific percentage. What's stable across every credible source is the shape of the curve. ChatGPT down, Gemini up sharply, Claude up from a small base. That shape has now shown up in three independently run studies with three different sampling methods. That's about as much agreement as you're going to get on a market this volatile.
The mistake: building a budget around one tracker's number
Here's where this becomes a decision problem instead of a trivia problem. We see teams walk into budget conversations with a single slide: "ChatGPT is at 46% share, so we're putting 46% of GEO spend there." That's precision theater. Swap in First Page Sage's 52.7% and the allocation moves by six points on a number nobody involved actually measured themselves. Pick whichever tracker's PR team got the best press cycle that month and you've built a budget on a coin flip between two firms that don't even agree on what "share" means.
The deeper problem is that a single blended "AI market share" number was never the right unit for a GEO decision in the first place. We made this case in detail in our piece on tracking AI visibility across engines separately rather than blending them: a blended figure averages away exactly the information you need, which is how your specific brand performs on each engine your specific buyers actually use. ChatGPT dropping five points industry-wide tells you nothing about whether your brand's citation rate on ChatGPT is climbing or falling. Those two things aren't the same number, and they don't even move in the same direction half the time.
“Three trackers agreeing on direction and disagreeing by six points on magnitude isn't a data problem you can solve by picking a favorite source. It's a signal that the number itself isn't precise enough to build a budget on.”
This is also why we've argued for a per-engine investment framework instead of chasing the industry-wide leaderboard. If Gemini is genuinely the fastest-growing engine across all three trackers, and it is, that's a real signal worth acting on. But "how much budget goes to Gemini-specific optimization" should be answered by where your buyers show up and where your citation rate is weakest, not by whichever tracker's number happened to land in the deck this quarter.
What to track instead
None of this means ignore the industry numbers. Direction is real information: three independent methodologies converging on "ChatGPT losing share, Gemini gaining fastest, Claude crossing into double digits" is a genuine market signal worth factoring into where you invest attention. What it means is stop treating the specific percentage as precise enough to anchor a board slide or a budget split. Nobody, including Sensor Tower, Similarweb, and First Page Sage, agrees closely enough on the number for that to be defensible math.
There's a version of this that connects back to something we've written about separately: engine-level share is volatile in a way that category ownership within an engine is not. Even if you can't pin down whether ChatGPT is at 46% or 53% this month, the brands that have already built durable citation authority for their category tend to keep it regardless of which way the overall usage numbers move. That's arguably the more useful thing to be tracking than the leaderboard itself.
So do this next. Pull your own analytics and split AI-engine referral traffic by source for the last two quarters. Run a standing set of ten to twenty buyer-relevant prompts across ChatGPT, Gemini, Claude, and Perplexity today, and log who gets cited. Set a recurring monthly check on both. That's a market share number worth building a plan around, because it's the only one measuring the market you actually compete in. If you want a structured way to build that per-engine tracking into a real generative engine optimization program instead of a spreadsheet you update when a headline reminds you to, that's the work worth doing before the next tracker report resets the conversation again.
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Tyler leads work at the intersection of SEO and generative engines at Something Inc., helping B2B brands get ranked and cited across every major AI engine.