In the three years since the television industry’s biggest companies pitched their shows to advertisers in person at the so-called upfronts, the entertainment industry has been flipped on its head.For the first time in three years, the circus is coming back to town.The television industry’s biggest showcase for advertisers, the so-called upfronts, will return to Manhattan landmarks like Radio City Music Hall and Carnegie Hall after the pandemic put the glitzy, in-person galas on hold. Just like in the old days, media executives will make their best pitch to persuade marketers to buy tens of billions of dollars of commercial time in the coming months.But thanks to the vastly changed media industry, many aspects will be radically different. The companies themselves have changed: CBS merged with Viacom and then renamed itself Paramount Global, and WarnerMedia and Discovery completed a megamerger, forming Warner Bros. Discovery. The tech giant YouTube is making its debut on the presentation lineup this week, and there is already intrigue that Netflix could join the fray next year.And instead of unveiling prime-time lineups that will roll out in the fall, media companies are expected to spend a large portion of their time talking up advertising opportunities on streaming services like HBO Max, Peacock, Tubi and Disney+. There’s good reason for that: Advertisers are now allocating closer to 50 percent of their video budgets to streaming, up from around 10 percent before the pandemic, several ad buyers said in interviews. The free ad-supported streaming platforms Tubi and Pluto were highlights for their owners, Fox and Paramount, in the most recent quarter.“The upfronts used to be ‘Here’s 8, 9, 10 p.m. on Monday night’ — I don’t think anybody cares about that anymore,” said Jon Steinlauf, the chief U.S. advertising sales officer for Warner Bros. Discovery. “You’re going to hear more about sports and things like Pluto and less about the new Tuesday night procedural drama.”Stephen Colbert during the 2019 CBS upfront. CBS merged with Viacom and then renamed itself Paramount Global since the last time it was featured on an upfront stage.John P. Filo/CBSThe courtship is no longer one-sided, when reluctant streaming platforms once put a stiff arm to commercials. As subscriber growth starts to slow for many streaming services, advertising — a mainstay of traditional media — is gaining appeal as an alternative source of revenue.Netflix, which resisted ads for years but is aiming to debut an ad-supported tier later this year after a subscriber slump, is expected to play a larger role in future upfronts. Disney+, which has so far continued to increase its subscriber count, said this year that it would also offer a cheaper option buttressed by ads.“Streaming is part of every single conversation that we have — there isn’t an exception based on who your target it is, because whether you’re targeting 18-year-olds or 80-year-olds, they’re all accessing connected TV at this point,” said Dave Sederbaum, the head of video investment at the ad agency Dentsu. Last year, ad buyers spent $5.8 billion on national streaming platforms, an amount dwarfed by the $40 billion allocated to national television, according to the media intelligence firm Magna. But television sales peaked in 2016 and are expected to decline 5 percent this year, compared with a 34 percent surge projected for streaming ad revenue as services offer more preproduced and live content.The rapid changes in viewing habits have caused many marketing executives to shift toward ads placed through automated auctions and “away from legacy models like upfronts” where “advertiser choice is limited,” said Jeff Green, the chief executive of the ad-tech company The Trade Desk.“As advertisers are seeing reach and impact erode from traditional cable television, they are focused on moving to premium streaming content,” he said during his company’s earnings call last week. “Increasingly, this is the most important buy on the media plan.”But streaming will not be the only topic at the upfronts — the events themselves will also be center stage.After two years of upfront pitches recorded from executives’ living rooms, buyers will fly into New York from around the country. They will shuttle among grand venues to watch presentations while seated alongside their competitors. Some venues are asking for proof of vaccination, while masks are a must at some; Disney is requiring a same-day negative Covid test.To many networks, hosting an in-person upfront was nonnegotiable this year.“This show cannot be too big,” Linda Yaccarino, the chairwoman of global advertising and partnerships at NBCUniversal, said she told producers of the company’s presentation at Radio City Music Hall on Monday. “Having everyone in the room together, there is no surrogate for that.”“Every single brand and marketer and advertiser comes in for the upfront week,” said Rita Ferro, the president of Disney advertising sales and partnerships. “It’s going to look and feel very different because it is very different — there’s so much more that we’re bringing to the stage.”Many of the week’s showcases will eschew a detailed rundown of nightly prime-time schedules and instead offer a more holistic view of available content platforms.Mr. Steinlauf, the Warner Bros. Discovery advertising chief, who is a veteran of several decades of upfronts, described changes that represent “the biggest shift of my career.” He said streaming was “the future, the new frontier,” and heavily watched athletic events were “the new prime time.” Warner Bros. Discovery will make its upfronts debut on Wednesday in front of 3,500 people at Madison Square Garden.Jo Ann Ross, Paramount’s chief advertising revenue officer, said that its event on Wednesday would “show a broader look.” She described it as a “coming-out party as Paramount” for the company formerly known as ViacomCBS.“It will feel different than what it was in the past,” she said.On Tuesday, Disney will abandon its usual upfront home at Lincoln Center and move to a space in the Lower East Side at Pier 36. The presentation will feature its three streaming platforms — Hulu, ESPN+ and Disney+ — sharing a stage for the first time. NBC Universal will highlight its technological capabilities, such as data collection, while also drumming up its Peacock streaming platform, even though the service already made a pitch earlier this month during NewFronts, an event for digital companies courting Madison Avenue.Linda Yaccarino of NBCUniversal said that “having everyone in the room together” this year for the company’s upfront was the only way to go.Tawni Bannister for The New York TimesThe competition could mean more demands from advertisers, like the ability to back out of commitments and lower thresholds for how much buyers must spend.“It’s basic economics — there are now more options available to media buyers and so you’re going to see a lot more willingness to be flexible,” said David Marine, the chief marketing officer of the real estate company Coldwell Banker.Potential headaches for advertisers this year could include Russia’s war in Ukraine, global supply issues and steep inflation, according to Magna. But low unemployment and other signs of strength from the U.S. economy, along with the coming midterm elections, are expected to feed a surge in ad spending.How the upfronts address those concerns, along with deeper movements in the industry, “will be telling,” said Katie Klein, the chief investment officer at the agency PHD.“There’s always going to be room for the upfront, there’s always going to be a need for it,” she said. “But it’s going to evolve as our industry is evolving.” More