June 2 (Reuters) - OpenAI's ChatGBT app has surpassed 1 billion monthly active users worldwide, becoming the fastest app ever to reach that milestone.

This record figure, reported by market analytics firm Sensor Tower, comes amid growing competition between Anthropic and OpenAI for control of the rapidly expanding artificial intelligence market.

SensorTower said that ChatGBT reached 1 billion monthly active users in May, nearly three years after its launch, surpassing the pace set by apps such as Google Maps, TikTok, Instagram and YouTube.

The company said that ChatGBT users in the United States who downloaded Anthropic's Cloud app in the first quarter of 2026 spent 5 percent less time on ChatGBT one month after downloading than their average usage in the previous eight months.

Anthropic filed a confidential application for an initial public offering in the United States on Monday, while Reuters reported that OpenAI is also preparing to file for an IPO in the coming weeks.

Sensor Tower data indicates that Cloud had 56 million monthly active users worldwide as of the second quarter of this year, while its annual monthly active user growth rate of approximately 640 percent exceeded ChatGBT's user growth rate of 62 percent.