ChatGPT reached 640.68 million monthly active users in June 2026, according to Similarweb data shared July 17. The figure marks a record, up 2.2 percent from May and 24 percent from June 2025. Similarweb’s tracking shows the metric has declined only three times across the past 37 months, a run of near-continuous growth.
The number matters beyond raw scale. Monthly active users is the denominator behind ChatGPT’s citation visibility: the size of the answer surface competing with classic search results for a query’s first and only response. As that base expands, more queries route through ChatGPT instead of a search engine, and more of the visibility fight for GEO (generative engine optimization) practitioners shifts toward what ChatGPT chooses to cite.
Similarweb’s figure is one vendor’s measurement panel, not audited data from OpenAI itself. The company has not published its own monthly active user counts for comparison. Teams tracking ChatGPT citation share should treat this total as directional and pair it with their own referral-traffic and prompt-visibility monitoring rather than as a verified platform metric.
Similarweb shared the ChatGPT monthly active user estimate on July 17, 2026.
