Google announced in August 2026 that the Gemini App passed 1 billion monthly active users; OpenAI announced on October 7 that ChatGPT passed 1.2 billion weekly active users. The dates and metrics differ, so neither number declares a winner.

Actually, these two numbers measure different things. This piece won’t pick a winner; it shows you how to read the metric behind each number. If you want to first get to know the company behind Gemini, read What kind of company is Google.

Trap One: Monthly Active vs Weekly Active

Monthly active users (MAU) are people who used a product at least once in a month. Weekly active users (WAU) are people who used it at least once in a week. People who come back every week are always fewer than people who use it once a month, so two numbers with different bars can’t be compared by size.

Each number only describes its own scale of use; neither proves who is ahead.

Trap Two: Who Counts as “Having Used It”

ChatGPT’s users are people who actively open it to chat. Google’s numbers mix several kinds. Gemini App users are closer to active use. The AI summaries on search results pages (AI Overviews) were announced in May 2026 as seen by 2.5 billion people. AI Mode, the chat mode inside Search, was announced in July 2026 as passing 1 billion monthly actives, and Google now merges the two into one search experience.

Seeing a summary and actively chatting are different kinds of use. A 2025 Pew Research Center study found that in search visits with an AI summary, about 1% clicked a link inside the summary and 26% ended their browsing; this doesn’t prove users didn’t read or use the summary.

Trap Three: Is the Growth Pushed or Chosen

Google’s Search, Android, YouTube, and Gmail each have billion-scale users, and Gemini can be placed straight into these entry points without users downloading anything. OpenAI has no such advantage. But it also means part of Gemini’s user count is “pushed”: for example, the old voice assistant on Android phones was replaced by Gemini, and many people never actively chose it.

This embedded growth has also drawn regulators. In July 2026, the EU issued a decision under the Digital Markets Act (DMA) requiring Android to open 11 system features that Gemini uses to other AI assistants as well.

What the Third-Party Numbers Say

According to a June 4, 2026 report by El País / EFE, Sensor Tower estimated ChatGPT at about 1 billion monthly actives in May, and the Gemini App at about 472 million for the second quarter to date.

Third-party estimates and Google’s own figures differ in date, method, and scope, so the gap can’t be blamed entirely on how each side counts. Also, an early-2026 report from a16z found that about 20% of ChatGPT’s weekly active web users also use Gemini in the same week, so the two look more like tools people use side by side than a choice of one or the other.

So Who Actually Wins

It depends what you compare. On the number of active users and depth of use, third-party data leans toward ChatGPT in the lead. On breadth of reach, Google’s embedded scale through Search and Android is larger. No third party can currently use one ruler to measure both ChatGPT’s users across all platforms and the true de-duplicated total of Gemini plus Search’s AI features.

Penchan’s summary

Every company reports the metric that makes it look best. That isn’t lying, but it misleads anyone who doesn’t look closely.

Carry three rulers with you: “monthly active vs weekly active,” “active vs passive,” and “standalone app vs embedded service.” Next time you see a “so-and-so overtakes so-and-so” headline, measure it before you believe it. This method works for the user numbers of every AI platform.

Further reading: What kind of company is Google, How to choose across the Gemini family, Where Google’s antitrust case stands.