Sensor Tower: Meta’s Muse app tops 10 million US downloads in 40 days

Meta's Muse app has reached 10 million downloads in the United States within 40 days of launch, and it is only the 12th app to do that since Sensor Tower began tracking apps in October 2015. That is the finding in 9to5Mac's report by Marcus Mendes, published October 20, 2026, at 1:45 pm PT. Sensor Tower also says Muse is outpacing ChatGPT, Claude, and Grok on user retention.

This piece is for readers who follow AI assistant apps, US App Store rankings, and mobile ad spending. It covers Muse's first 40 days against ChatGPT, Grok, and Claude, ChatGPT's early global download mix, current free-app ranks, 7-day and 14-day retention, the share of Meta's US advertising spend going to Muse, and the privacy finding that led Meta to suspend the app's sharing feature.

Sensor Tower: what actually changed

A few weeks ago, Sensor Tower reported that Muse had surpassed 5 million US downloads, thanks to a mix of popularity and Meta's massive ad push. The app had spent 12 consecutive days at the top of the US App Store. It has since slipped to second place. The 40-day total is the new milestone: Sensor Tower says Muse is just the 12th app to reach 10 million US downloads within 40 days of launch since the firm began tracking apps in October 2015.

Sensor Tower says ChatGPT, Grok, and Claude reached just 3.7 million, 500,000, and 200,000 US downloads, respectively, in their first 40 days. ChatGPT "scaled to ~15mn global downloads in its first 40 days post app-launch, as its global reach expedited its growth." The US, Japan, Brazil, and Germany accounted for 25%, 9%, 6%, and 5% of those global downloads. Sensor Tower did not name them all. Nine were mobile games, and the most recent was Meta's Threads in July 2023.

Sensor Tower: how it works

Sensor Tower links the earlier climb past 5 million US downloads to a mix of popularity and Meta's massive ad push, and Meta is still spending heavily. Muse accounted for 39% of Meta's advertising spend in the United States so far this month, up from 23% in September. Among US brands ranked by advertising impressions, Muse climbed from 73rd to 21st. Those are the promotion figures Sensor Tower published with the 10 million US download count on October 20, 2026.

Retention is the second series in the report. Sensor Tower says US Muse users are returning to the app, averaging a 30% retention rate after 7 days and a 23% retention rate after 14 days. ChatGPT, Claude, and Grok averaged a 19% retention rate at 7 days and a 16% retention rate at 14 days. Meta is ahead of those three AI apps at both marks. Marcus Mendes wrote that the gap is not surprising, because this is one of Meta's strongest suits.

Sensor Tower: why it matters now

Only 12 apps have reached 10 million US downloads inside 40 days since October 2015, and nine of the earlier apps were mobile games. The most recent before Muse was Meta's Threads in July 2023. The new report also lands in a softer US stretch for ChatGPT: its US downloads declined 25% over the past 30 days compared with the previous 30-day period. ChatGPT is still the fourth most downloaded free app on the US App Store. Claude ranks seventh. Grok ranks 34th.

Muse held the top spot on the US App Store for 12 consecutive days and has slipped to second, yet users come back at 30% after 7 days and 23% after 14 days, above the 19% and 16% averages for ChatGPT, Claude, and Grok. The same report carries fresh privacy concerns. Security researchers discovered that shared conversations could expose sensitive personal and business information, and Meta has suspended the sharing feature while it investigates. Sensor Tower still published the download milestone and the retention lead beside that suspension.

Sensor Tower: who is affected

US Muse users are the people in the 10 million download count and in the 30% and 23% retention rates, and they are the people who could share a conversation. Security researchers discovered that shared conversations could expose sensitive personal and business information. Meta has since suspended the sharing feature while it investigates the issue. The October 20, 2026 report places that suspension beside Sensor Tower's retention lead and gives users no date for sharing to return. The investigation remains open.

ChatGPT, Grok, and Claude are the comparison apps, with first-40-day US downloads of 3.7 million, 500,000, and 200,000 respectively, set against Muse's 10 million. Their averaged retention is 19% at 7 days and 16% at 14 days. ChatGPT's separate global total was about 15 million in that first 40 days, and the US, Japan, Brazil, and Germany made up 25%, 9%, 6%, and 5%. Muse is also 39% of Meta's US advertising spend so far this month, up from 23% in September.

Sensor Tower: what to watch

Meta's spend share is still month to date. Muse accounted for 39% of Meta's advertising spend in the United States so far this month, up from 23% in September, and it rose from 73rd to 21st among US brands ranked by advertising impressions. Both the spend share and the impression rank come from the October 20 report. ChatGPT's US downloads are down 25% over the past 30 days versus the previous 30-day period. ChatGPT is fourth, Claude is seventh, and Grok is 34th among free apps on the US App Store.

The suspended sharing feature is the open product issue. Meta suspended it after security researchers found that shared conversations could expose sensitive personal and business information, and the company is still investigating. The record Sensor Tower published with that pause is 10 million US downloads in 40 days, second place on the US App Store after 12 days at the top, and retention of 30% after 7 days and 23% after 14 days. The report sets those figures next to the privacy suspension.