US adults are finally expected to spend more time with their phones and tablets than watching traditional TV, like broadcast and cable, eMarketer forecasted in a report on Wednesday.

The data marks a long-awaited milestone. Mobile usage has been rising, and traditional-TV usage falling, among US adults for at least the past five years, based on the firm's estimates.

It comes as people have more options for watching video online, including programming from traditional TV companies like Disney and WarnerMedia that are launching their own streaming services.

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Legacy media giants Disney, WarnerMedia, and NBCUniversal are all rolling out streaming services in the next year that will make it easier for people to watch their programming without going through traditional TV providers, like a cable service.

They're joining companies like CBS, which launched a streaming outpost for its broadcast network in 2014, and cable staple, Fox News, which recently debuted its own online platform, Fox Nation.

A new report from eMarketer explains why more traditional media networks are placing big bets on streaming video now, after years of US customers "cutting the cord," or canceling conventional TV services.

This year, in a first, the average US adult is forecasted to spend more time using mobile devices than watching conventional TV, including broadcast, cable, or other over-the-air channels live or on DVR, according to research firm eMarketer.

US adults will spend an average of 3 hours and 43 minutes per day on mobile devices, not including voice calls, the company projected in a report on Wednesday. They'll spend a few minutes less per day — 3 hours and 35 minutes on average — watching traditional TV.

Americans are still spending plenty of time watching video, though.

Across devices, such as smartphones, TV sets, or desktop computers, US adults are forecasted to spend an average of 5 hours and 12 minutes per day watching video in 2019, in line with last year.

More traditional TV networks are making their content available over the internet to keep up with the rising tide of customers who are watching TV in unconventional ways, such as via apps on their smartphones or smart TVs.

The eMarketer forecast for traditional TV marks a long-awaited milestone. Mobile usage has been rising, and traditional-TV usage falling, among US adults for at least the past five years, based on the research firm's estimates.

"We've expected that mobile would overtake TV for a while, but seeing it happen is still surprising," Yoram Wurmser, principal analyst at eMarketer, said in a statement. "As recently as 2014, the average US adult watched TV nearly 2 hours longer than they spent on mobile devices."

The marker also comes as streaming giants like Netflix, Hulu, and Amazon release more original programming that competes with traditional TV shows, and more online alternatives to cable TV arise, like the streaming bundles from YouTube TV and Hulu with Live TV.