The new season of "Sesame Street" premieres on HBO on Jan. 16th. The episodes will air on PBS 9 months later. (HBO)

The iconic Muppets of “Sesame Street,” who spent the past 45 years on PBS, will reveal a host of modern touches when they debut Saturday morning at their new home on HBO. Elmo will move into a brownstone, the Cookie Monster will team with some tablet-wielding crime-fighters, and Oscar the Grouch will pop out of not just trash cans but recycling and compost bins, too.

Oh, and another thing: You’ll have to subscribe to HBO to watch it.

Yet the biggest changes for America’s best-known children’s series are much subtler — and riskier — than can be seen on set at 123 Sesame Street: Shorter episodes, fewer characters and a sharper focus on winning the millions of preschoolers who don’t get the show turned on for them, but choose it themselves, via a phone or tablet app.

A lot has changed since the psychedelic “Sesame Street” first hit family living rooms in 1969, becoming a mainstay of public television and ushering in an age of “nutritious entertainment.”

So as the battle for kids’ attention heats up, the American classic is having to become a different beast: redesigned, relentlessly field-tested and repositioned to win that increasingly lucrative market, the media-drenched toddler of 2016.

“It’s a very competitive marketplace . . . and it really is the kids now who are making the decisions,” said Carol-Lynn Parente, the show’s executive producer. “ ‘Sesame’ is the most-tested show in the history of television. We’re trying to diagnose what makes these kids tick.”

“Sesame Street’s” 46th season will be its first to premiere behind HBO’s premium-cable paywall, where episodes will run exclusively for nine months before they’re made available on PBS.

It will also be the first to fully break with its long-standing hour-long format and shrink to 30 minutes, to keep kids with other media vying for their attention focused and engaged. That half-hour will also be newly focused on a single backbone topic — a departure from the hour-long “Sesame,” which could flit between Elmo’s songs, the central “Street story” and “Abby’s Flying Fairy School” in a squeaking blur.

The show’s opening theme song will still wonder how to get to Sesame Street, but with a tempo that is faster and more upbeat, and with slickly cinematic, slow-motion shots that seem pulled straight from TV. The show will also devote story lines to far fewer characters than previous puppet-filled episodes, a “commitment to the top characters” designed to keep kids coming back.

Where recent series focused on STEM (science, technology, engineering and math) skills and childhood obesity — most notably, with Michelle Obama joining Big Bird in the White House kitchen in 2013 — new shows will focus on lofty goals such as teaching kids “self-regulation” and “executive function”; in other words, handling challenges without having a meltdown.

Leading the curriculum will be the insatiable Cookie Monster: As “Sesame” spokeswoman Alicia Durand said, “He’s the poster child for self-regulation skills, because he has none.”

“Sesame” will still teach the basics: The vampiric Count von Count will still count, and kids will still be taught a “Letter of the Day”: In the first new episode, “Black-ish” actor Tracee Ellis Ross will teach the letter B while in bed with Boodles, her stuffed beagle.

But more and more, the episodes will focus on scenarios that children born in the Internet age will no doubt confront. One recent episode involves Elmo and Abby scheming to get a character to stop staring at her phone.

“Sesame’s” five-year contract with HBO, announced in August, was a lifeboat for Sesame Workshop, the show’s nonprofit parent organization, which lost $11 million in 2014 largely because of plunging sales of DVDs, its biggest moneymaker. But the deal, whose financial terms were not disclosed, was also a crucial win for HBO, the not-so-family-friendly cable empire looking to boost its appeal in kids’ entertainment.

But the unexpected marriage also fueled a major backlash. For critics, the premium-cable giant’s swallowing of a children’s show designed to deliver free education to underprivileged kids was, as comedian Brian Gaar tweeted, like “privatizing a national treasure.”

Others bemoaned that Elmo would soon share the same airwaves as grittier shows such as “Game of Thrones.” Parents Television Council President Tim Winter said that “Sesame”-charmed parents would be forced to “subscribe to the most sexually explicit, most graphically violent television network in America.”

The producers feel the pressure with every change to the American classic, and they’re expecting this season to face more inspection than ever. Sesame Workshop creative director Brown Johnson called it exciting but “kind of terrifying.”

“There’s always a danger that one of the changes will alienate people,” said Parente, the executive producer. “It’s something other properties don’t have to deal with: the deep emotions of this brand . . . the challenge to stay relevant, and to stay important to preschoolers, too.”

Where parents were once “the first door-openers for ‘Sesame Street,’ ” producers said, two-thirds of children now first see the show via an online streaming service or on demand. Because so many kids watch on tablets or cellphones, producers last season placed a heavier emphasis on crafting shots so they’re best viewed on smaller screens.

And because children are making the choice to watch, producers have inched away from the types of cheeky pop-culture references once included as winks for their parents. They are less likely to watch anyway, producers said — where half of all American children had a stay-at-home mom in 1960, only 14 percent of kids had one in 2014, Pew Research data show .

To keep up with its toddling audience, “Sesame’s” creators have worked with developmental psychologists and early education specialists to research how kids learn and what they like.

They also continue to invest in “distractor testing,” watching where kids gravitate when “Sesame” is turned on in a room full of toys, or across from a TV playing the competition. One researcher per child will record where the kids are looking at the screen, or gauge how distracted they are.

“My first rule is know your audience . . . and we have very tough critics,” said Johnson, a longtime Nickelodeon veteran who guided that network’s “Blue’s Clues” and “Dora the Explorer.” “If they don’t understand what’s going on or what’s happening in the story, they’ll basically walk away.”

Pressure to update “Sesame Street” has grown as more alternatives have hit the market. Producers no longer just have to contend with TV franchises such as Mickey Mouse and “Paw Patrol,” they must now also face down streaming giants who see kids’ shows as a way to get cord-cutting families onboard.

Netflix, which last week expanded worldwide, owns franchises such as “Reading Rainbow,” is rebooting “Inspector Gadget,” and plans to debut 30 original kids’ programs as part of a $5 billion content spending spree this year.

But “Sesame’s” segment-heavy magazine format was always well attuned to shorter, more “snackable” entertainment, a saving grace in a time where shorter online videos are all the rage. That could help explain why “Sesame Street” has been such a hit on YouTube, attracting 2.4 billion views since 2006, including a billion just last year.

“We live in a media-competitive world, and that’s why we have to spend time listening to children, observing children and constantly evolving,” said Rosemarie Truglio, Sesame Workshop’s vice president of education and research. “The child has not changed, but their environment has changed, and they can get ‘Sesame’ whenever they want.”