In a historic first, the market tracker company expects "linear TV" (conventional broadcasting and cable) to account for less than half of daily viewing, dropping to under three hours while average daily digital video watching climbs to 52.3 percent with 3 hours and 11 minutes.
"This milestone is driven by people spending more and more time watching video on their biggest and smallest screens, whether it's an immersive drama on a connected TV or a viral clip on a smartphone," Insider Intelligence principal analyst Paul Verna said in a release.
"Given teens' preferences for social and streaming video over TV, we can expect these trends to continue to shift in favor of digital."
Netflix and YouTube are "neck and neck" leaders when it comes to digital video audience attention, with US adults tuning in for about 33 minutes daily on average at each platform, according to Insider Intelligence.
Live sporting events becoming available on video streaming platforms is also helping power the shift away from traditional television, as is the popularity of shared video clips on apps, the market tracker said.
TikTok is a key driver with the average amount of time spent there daily by US adults climbing sharply, according to Insider Intelligence.
"TikTok versus Netflix will be a major trend to watch this year," said Insider Intelligence principal analyst Jasmine Enberg.
"The lines between social and entertainment have blurred, and TikTok is now coming for the bigger-screen video players."
TikTok CEO Shou Zi Chew will testify in March before US lawmakers in Washington, where the Chinese social media app faces accusations that it is beholden to the Communist Party in Beijing.
TikTok, whose parent company ByteDance is Chinese, is fighting for survival in the United States with rising calls from mainly Republican lawmakers that the company should be outright banned because of its alleged links to Beijing.
Insider Intelligence noted that while Twitter is not primarily a video platform, overall time spent on the platform by US adults is expected to drop this year and next year as its ranks of users decline.
"The problem is that Twitter's efforts to encourage more original videos, from Vine to Fleets, have so far been unsuccessful," Enberg said.
"Twitter owner Elon Musk's attempts to bring more video to the app, including potentially incentivizing YouTube creators to post to Twitter, will be futile at improving time spent among all US adults unless he also manages to stave off a user decline."