Matching with same-sex partners over the internet is often far safer and more convenient than trying to do so in person.
The internet thus helps those with similar, and sometimes quite specialised, views on what makes for good sex, or indeed on more or less anything else.
The business is worth $4.6bn globally, growing fast and highly competitive.
Match Group, which operates Tinder, the original and some 40 similar businesses, had revenues of $1.3bn in 2017—a similar figure to the revenues of American condom sellers.
Bars and restaurants have fallen since (see chart).