At an adoption rate of 5m per week.
The retro photo app passed 40 million users just a fortnight ago and has now reached the 50 million mark, according to Mashable.
The sudden surge has come following a launch on Android at the start of the month, with added interest driven by Facebook's $1 billion buyout.
It's an impressive rise, given that the app started the year with just 15 million users, all of which were on iOS.
It also appears to contradict the fear of a drift away from the app by users who objected to its purchase by Facebook.
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