Only 12 apps have reached 10 million U.S. downloads within 40 days of launch, according to Sensor Tower data tracking from October 2015 onward. Nine of those 12 were mobile games, a category known for rapid viral distribution. The question hanging over Meta’s Muse is straightforward: does it belong in that company because people genuinely want it, or because Meta has the advertising infrastructure to manufacture a launch event at scale?
Rare Company, Familiar Name
Muse reached a download threshold that almost no non-game app has managed, but the competitive comparisons require some care.
Sensor Tower, via TechCrunch, reported that Muse recorded 10.2 million U.S. downloads and 10.9 million globally during its first 40 days after launching in September 2026. The only recent non-game app to reach this threshold was Meta’s own Threads, which hit the mark in July 2023. For context, ChatGPT reached approximately 3.7 million U.S. downloads in its comparable early window; Grok reached 500,000; and Claude reached 200,000, per 9to5Mac. ChatGPT’s often-cited figure of 15 million downloads in its first 40 days reflects global distribution and is not a direct comparison, since Muse launched only in the United States and Canada.
Retention Adds a Different Data Point
Download totals tell you how many people showed up; retention data begins to tell you whether they stayed.
Muse recorded 30% seven-day retention and 23% fourteen-day retention in Sensor Tower’s tracking. Its main AI competitors, including ChatGPT, Claude, and Grok, averaged 19% at seven days and 16% at fourteen days, according to 9to5Mac. Those figures indicate users are returning, but they do not establish whether Muse is anyone’s primary AI assistant or simply an app people open occasionally.
The Ad Budget in the Room
Meta’s promotional spending was substantial enough to complicate any reading of Muse’s organic demand.
Meta allocated 39% of its U.S. advertising spend to Muse in October, up from 23% in September, per 9to5Mac. The app climbed from 73rd to 21st among U.S. brands ranked by advertising impressions. The available data does not separate paid acquisition from organic installs, so the true split between Meta’s marketing reach and genuine word-of-mouth remains unclear.
Muse reached 2.5 million daily active users on October 16, a 15% week-over-week increase according to TechCrunch, which points to some momentum alongside the paid push.
A Privacy Problem That Needed a Quick Fix
A security flaw in Muse’s conversation-sharing feature exposed sensitive user information before Meta moved to suspend it.
Researchers at Claroc discovered that conversation-sharing URLs were discoverable through passive DNS searches, a flaw reported by Engadget. They enumerated approximately 6,800 shared-chat links and accessed information that included a small-business loan application, a bank-fraud alert with partial account information, and internal company documents. Meta suspended the feature while reviewing the report; Claroc later confirmed that previously accessible links were no longer opening. No specific regulatory action has been identified following the incident.
What the Next 40 Days Actually Measure
The launch numbers are strong, but the more meaningful data arrives once promotional spending normalizes and the conversation-sharing feature returns in some revised form.
The milestone is real, and the retention numbers are genuinely stronger than the competition’s early benchmarks. Whether Muse holds its user base once Meta’s ad tailwind subsides, and whether it can restore trust around shared conversations, is the story the first 40 days cannot answer.
