Roblox discloses few figures, but boasts 80 million players (active per month) in more than 30 countries. Most of them are 9 to 12 years old, while creators usually have more than 16. Mr. Misner says that Roblox spends almost no money on advertising; word-of-mouth was enough to make it the most popular entertainment platform for 6-12 year-olds, according to an estimate by Comscore.

This is not the first metajue, with a universe that allows players to create, but it is probably the first time it works as well, said Lawrence Michaud, director of studies for the think tank Idate. Roblox derives its revenue from user spending. The application and most games are free, but you have to buy Robux, the virtual currency, to customize your avatar or acquire elements to progress in an adventure. The best developers can also earn money. Alex Balfanz, a 19-year-old American, has created several games before experiencing a blazing success with Jailbreak (Escape), launched in April 2017, according to the American website Business Insider. In less than a year, he has raised over a million dollars.

More than a game, Roblox is a platform of creation. Once registered on your PC, mobile or Xbox One console, the user can be mistaken for a budding developer. Roblox provides him with very simple tools to quickly compose a game with a fairly graphic appearance. He can dig into a library of universes already built (a modern city or Far West, a castle, a prison), objects already modeled (cars, trees, trains) and choose his style game (shooting game, racing cars, sports, survival etc.).

Once finished, the game is on the Roblox distribution platform. It is not mandatory to be creative to have fun. Roblox says that just over a million people have created tens of millions of titles, accessible with a simple click on its website. But in the vast majority, these games are not finished, not very functional, even totally uninteresting.

Many are content to reproduce, with much less resources, already existing successes, such as Mario or Pokemon. But some creations have managed to pull in the game. Jailbreak, which allows to embody a fugitive prisoner or a police officer in pursuit, is one of the most popular titles of the platform. He reported to his creator, aged 18, enough to pay four years of university studies.

Because if it is free access, the Roblox platform is full of micropayments. The avatar of the player, which will be the same in all games, is customizable against the virtual currency of the platform, Robux (400 Robux worth 5 dollars, just over 4 euros). Creators can also make access to their game pay which is rare or incorporate mechanisms that force players to spend Robux.

And it works. In the first half of 2018, the only mobile version of Roblox would have generated 210 million dollars. The app oscillates between the 15th and 30th place of the most lucrative video games on the smartphone in the United States, according AppAnnie Institute. The platform says to donate a portion of its income to creators: this sum is expected to reach $ 70 million this year. But to become millionaires before their baccalaureate, aspiring developers must put their hands in their pockets.