The scale is no accident. Meta has marketed Muse across its family of apps, which counts 3.6 billion daily active users, and is also spending heavily on conventional advertising: 39% of Meta's total ad spend in October went to promoting Muse, up from 23% the month before. That push has lifted Muse to the 21st largest US brand by advertising impressions this month, from 73rd in September.

Marketing alone does not keep users, but Muse's retention figures suggest people are sticking around. Sensor Tower's data shows a 30% US retention rate after seven days and 23% after fourteen, against averages of 19% and 16% for rivals ChatGPT, Claude and Grok. Daily active users reached 2.5 million for the first time on October 16, a 15% week-over-week rise.

The download comparison with competitors is lopsided in Muse's favour at home: ChatGPT managed 3.7 million US downloads in its first 40 days, while Grok and Claude saw 500,000 and 200,000 respectively. Globally it is a different story, with ChatGPT at around 15 million, though that is not a like-for-like contest since Muse is only available in the US and Canada while ChatGPT drew users in Japan, Brazil, Germany and beyond. Muse has held the No. 1 spot on the US App Store every day except October 19, when the streaming app Kick briefly edged it out, and has topped Google Play over the past 30 days.

There is a wrinkle worth remembering as the app scales: Muse can handle tasks on users' behalf, and that agentic behaviour has already caused friction. In September, Amazon blocked the agent from shopping on Amazon for its users, citing its Conditions of Use and raising privacy and security concerns that Muse browsed without identifying itself.