Internet-delivered TV is the new front in the war for viewers' attention spans.

Netflix, the online movie rental company, is following up on the $100 million drama "House of Cards," the political thriller starring Kevin Spacey and Robin Wright, with four more series this year. Microsoft is producing programming for the Xbox video game console. Other companies, from AOL to Sony to Twitter, are likely to follow. The companies are, in effect, creating new networks for television through broadband pipes and also giving rise to new rivalries - as between Amazon and Netflix and with the broadcast networks as well.

Amazon is making pilot episodes for at least six comedies and five children's shows. Sometime this spring it will put the episodes on its Amazon Prime Instant Video service and ask its customers which ones they like, then order full seasons of some of them.

Netflix has been ordering entire seasons of its shows without seeing pilots first. Reed Hastings, Netflix's chief executive, said that "House of Cards" had been a "great success" for the company. Its next program, a horror series called "Hemlock Grove," premieres in April.

Microsoft has said little about its plans. But all three companies are commissioning TV shows because they have millions of subscribers on monthly or yearly subscription plans. Though the shows may lose money in the short term, having exclusive content increases the likelihood that existing subscribers will keep paying and that new ones will sign up, bringing in more money in the long run.

The trend may leave cable TV companies with subscribers who will decide there's enough to watch online. At the same time, the rise of Internet-only shows may make viewers more dependent on the broadband cord, which often is also supplied by the cable company.

These shows look and feel like traditional TV. That is partly because more viewers are watching Internet content on big-screen TV sets, but it is mostly because the companies involved are throwing money at the projects: each of the Amazon comedy pilots cost the company upward of $1 million, which is less than the $2 million invested in a broadcast comedy pilot, but more than is typically invested in cable pilots.

Analysts say they expect more TV investment to come, including from companies that do not have monthly subscribers to please. YouTube, for instance, the biggest video Web site of all, makes its money from ads, not from subscriptions. But it has paid dozens of outside producers to start channels so that it has original, professional content. And its owner, Google, can afford to pay many more.

DirecTV, the biggest satellite distributor in the United States, is planning to introduce its first homegrown show, a thriller called "Rogue," next month.

One result of all these ventures may be too much TV. Christy Tanner, the chief executive of TVGuide.com, said viewers are already having trouble.

In surveys some complained "it feels like work" and that they grew "afraid of missing something," she said. "Viewers find organizing and managing all of their beloved TV options to be a bit stressful."

The New York Times