The Silicon Valley companies that make money off social media and online services have started to enact strong measures against extremism, barring white nationalists, white supremacists, neo-Nazis and others who follow creeds they deem racist and hateful.

Facebook and Twitter have developed tools to allow users to report hate speech and harassment. PayPal has blocked hate groups from using its financial services, and the ride-hailing services Uber and Lyft have urged drivers to report unacceptable customers. Airbnb took steps to stop white nationalists from renting rooms through its app before their gathering in Charlottesville, Va.

Most remarkably, perhaps, the efforts have even spread to the free-wheeling world of dating apps, where users have for years been welcome to screen potential lovers based on everything from height to religious beliefs.

The shift toward tighter regulation became especially clear after the Aug. 12 rally in Charlottesville led to violence. Days later, the dating site OKCupid announced on Twitter that it had banned a newly famous white nationalist.