Meta Platforms spent the past month marketing an AI companion app the way a consumer goods company markets a new detergent. In October it put 39 percent of its advertising budget behind Muse, up from 23 percent in September, and the app climbed to the 21st largest brand in the United States by advertising impressions, from 73rd a month earlier.
The spending bought scale. Muse drew 10.9 million downloads in its first 40 days, 10.2 million of them in the United States, according to estimates Sensor Tower published on October 20. Meta released the app on September 8.
That places Muse among a dozen apps that have reached 10 million U.S. downloads inside 40 days since October 2015. The rest of the list is mostly games: Fortnite, PUBG Mobile, Pokemon GO. Disney+ and Threads, Meta’s own text app, are the exceptions. Kara Lee, a senior insights analyst at Sensor Tower, said only 11 other apps have crossed that line that quickly, and Threads in July 2023 was the most recent.
Meta can manufacture a launch. Its family of apps reaches 3.6 billion people a day, and Threads was grafted onto Instagram’s social graph before it had a following of its own. Muse gets promoted inside Facebook and Instagram, and Meta bought the remainder of the installs.
The harder number sits further down the funnel. Sensor Tower estimates that 30 percent of U.S. users returned on day seven and 23 percent on day fourteen. ChatGPT, Claude and Grok averaged 19 percent and 16 percent over the same two windows. Muse reached 2.5 million daily active users on October 16, up 15 percent from the week before.
The download comparison is starker still. In their first 40 days, ChatGPT drew 3.7 million U.S. downloads, Grok 500,000 and Claude 200,000. Meta’s distribution turned a category that had grown by word of mouth into one that grows by placement.
Globally the picture is less flattering. Of the 10.9 million downloads, only about 700,000 came from outside the United States, a ratio that says as much about where the app has been promoted as about where demand exists. ChatGPT still reaches a larger audience abroad, and Meta’s promotion engine is strongest in the English-speaking markets where Facebook and Instagram already dominate.
Those figures come from modeled estimates built on panel data, not from audited company disclosures. Meta has not published Muse’s user counts, and Sensor Tower’s panel does not capture every install. The figures have not been independently audited, and the company has disclosed no numbers of its own.
Companion apps have a recognizable failure pattern: a spike at launch, then attrition as novelty fades and the conversation repeats itself. Replika built a large audience during the pandemic and lost part of it in 2023 when it restricted romantic role-play. Character.AI assembled a young and intensely engaged user base, then spent two years tightening the limits on it. Retention in this category tends to track product memory and persona quality rather than marketing.
Muse is pitched more broadly than a companion. Meta describes it as an agent that can carry out tasks on a user’s behalf, which puts it in the same conversation as ChatGPT and Gemini rather than in the narrower market for synthetic friends. That ambition is also why the retention figure carries weight inside the company. A tool that people use weekly justifies the data center spending behind it. A novelty app does not.
The regulatory file is open. In September 2025 the Federal Trade Commission ordered several companion chatbot operators to explain how they measure and limit harm to children and teenagers, and state attorneys general have opened their own inquiries. Strong retention among minors is a liability as much as an asset, and Meta’s own teen-safety record gives the question an edge that rivals do not carry.
Meta has raised capital spending on data centers and chips for three years running, and executives have argued that the returns appear as better ranking and higher ad prices rather than as standalone products. Muse gives that argument a consumer face, and gives the company something concrete to point to when investors ask what the spending buys.
Meta has not said how Muse will earn money. The app is free, and the company’s AI budget is funded by advertising, which is why the 39 percent figure reads as an investment rather than an expense line. If Muse can hold a daily audience, it becomes a surface for the same ads that already pay for Facebook and Instagram, and a source of the behavioral data that makes those ads work.
Forty days measures the marketing department. Day 30 and day 90 measure the product. Sensor Tower will publish both, and the interesting comparison will not be against ChatGPT’s launch but against Muse’s own October numbers. A companion app that keeps a third of its users for a week and a quarter for two has cleared the first bar. Whether it can hold them through the winter, when the advertising push ends and the app has to compete for attention on its own, is a different test, and the one Meta has not yet answered.
