A new era of à la carte television arrived in earnest this week — seemingly all at once and more quickly than many industry executives and television fans had expected. And with it, the virtual monopoly that cable, satellite and telecommunications companies have had over TV programming is dissipating.

Just one day after HBO said it would start an Internet-only offering, CBS announced on Thursday its own subscription streaming service that lets people watch its live programming and thousands of current and past shows on demand.

The moves signal a watershed moment for web-delivered television, where viewers have more options to pay only for the networks or programs they want to watch — and to decide how, when and where to watch them. Rapidly fading are the days in which people pay an average of $90 a month for a bundle of networks from a traditional provider.

Image Leslie Moonves of CBS said the streaming service was “an important part of our future.” Credit... Gus Ruelas/Reuters

“Everybody is talking about it,” Leslie Moonves, chief executive of the CBS Corporation, said in an interview. “It is an important part of our future. Our job is to do the best content we can and let people enjoy it in whatever way they want. The world is heading in that direction.”