The ChatGPT application developed by US artificial intelligence research organisation OpenAI, displayed on a smartphone screen in Berlin, Germany. (Image: EPA-EFE / Filip Singer) 
Shares of Alphabet GOOGL.O, which owns the Chrome browser, were down 1.6% in afternoon trading.
The product is the latest entrant in a fast-crowding field of AI browsers, which includes Perplexity's Comet and Opera's Neon, as companies weave in tools that can summarize pages, fill out forms and draft code to attract users.
Atlas lets users open a ChatGPT sidebar in any window to summarize content, compare products or analyze data from any site. In the agent mode in Atlas, ChatGPT interacts with sites for users, who can use it to do tasks from start to finish, like researching and shopping for a trip.
The browser is now available globally on Apple's AAPL.O macOS. It will soon be available on Windows, iOS and Android.
Led by entrepreneur Sam Altman, OpenAI upended the tech industry with the launch of its AI chatbot ChatGPT in late 2022. After its initial success, OpenAI has faced stiff competition from rivals including Google and startup Anthropic, and has been looking for new areas of growth.
Google integrated Gemini into its Chrome browser for users in the U.S. last month, and the iOS Chrome app will also have Gemini built into it.
A federal judge in September ruled that Google won't have to sell the Chrome browser.
It can keep paying partners to promote its search engine, Judge Amit Mehta ruled, noting that massive investment in generative AI — by Big Tech and startups — now threatens traditional search, making such payments more acceptable.
(Reporting by Juby Babu in Mexico City; Editing by Leroy Leo and Alan Barona)