The game is free because advertisers pay for your attention.
The game is free because your attention is the product, and sessions are shaped to deliver more ads.
Nothing: you are the audience being sold. The advertiser pays. In return you see banner ads, full-screen ads between rounds, or optional rewarded videos, and your device data may be used to target them.
On the web, portals sold banner ads against every pageview, so the games cost nothing and the pageviews paid the bills. Hyper-casual games (very simple games built for quick sessions) went further: buy an install for a few cents in a Facebook or TikTok auction, then sell that attention back as full-screen and rewarded video, betting that lifetime ad views beat the cost of getting you. Sessions shrank to under a minute, built to end in a death or a continue, either way an ad. Studios tested dozens of prototypes a week and killed anything that didn't retain players. Once ad revenue plateaued, the shop crept back as 'hybrid-casual'.
A banner on a free browser game is the mild end. With children, look out for full-screen ads, ads that look like game buttons, and what data the ad network collects.
Flash and Java turned any browser into a free arcade years before broadband was standard. Newgrounds opened its portal in 1999 and by 2000 submissions were so heavy that uploading had to be automated; Kongregate (launched 10 October 2006) went further, sharing ad revenue directly with the developers. From 2013 hyper-casual games stripped the shop out entirely. Flappy Bird was reportedly earning about $50,000 a day from adverts and sales at its January 2014 peak before its creator pulled it on 10 February 2014. Crossy Road passed $10 million in revenue and 50 million downloads within three months, largely through opt-in video ads. Subway Surfers made every death an ad break, and Hole.io was built purely to harvest ad impressions.
Historical prices and revenues are in US dollars at the time unless marked A$.
Dong Nguyen said Flappy Bird was earning about $50,000 a day from in-app adverts and sales at its January 2014 peak, before he pulled it from the App Store and Google Play on 10 February 2014.
Kongregate launched on 10 October 2006, sharing ad revenue directly with the Flash developers hosting games on the site.
Crossy Road passed $10 million in revenue and 50 million downloads within three months of its 20 November 2014 release, largely through opt-in video ads.
Subway Surfers (2012) was the most-downloaded mobile game of 2012 to 2019, crossing 2.7 billion downloads by December 2019 on App Annie's count.
Covered in Video Games & Money: Ep 31 · Hyper casual, Ep 18 · Browser.