After Bieber teased his next album during a surprise appearance at Coachella with Ariana Grande last month, YouTube announced that a top-secret new special from the pop star – who became famous as a teen on the video site – will premiere next year. 

"It promises to be one of the most talked-about YouTube originals ever," YouTube chief business officer Robert Kyncl said. 

The announcement came during YouTube's Brandcast presentation to advertisers Thursday  at Radio City Music Hall, where the site unveiled its new and returning slate of original series and specials, all of which will be made available for free – but with ads – starting this summer. That marks a departure from earlier shows that sometimes required a paid subscription.

Among other notable new offerings: a still-untitled Paris Hilton documentary due next year, directed by Alexandra Dean (PBS' "American Masters") that promises an "unvarnished" look at the heiress-turned-mogul. "Booktube," which started as a book panel discussion special with Michelle Obama, is a new series that spotlights prominent authors and notable personalities as they talk about their latest books. New episodes will be released monthly, beginning this summer. 

Grammy winner Alicia Keys was on hand to announce her new YouTube talk show, "Unwind," coming this August. 

"This show is super exciting because it's just about (laid-back conversation)," Keys said. "It brings together some of my fellow friends, artists and thought leaders, and we do it in this really unusual way."

YouTube also has a renewed emphasis on its homegrown YouTube celebrities, many of whom will star in  new shows and specials. Technology vlogger Marques Brownlee will unbox and review vintage products that defined pop culture in his new series "Retro Tech," premiering in December. Sports supergroup Dude Perfect, with nearly 41 million YouTube subscribers, will be followed on tour in an upcoming documentary, also premiering later this year. And YouTube gamer Mark Fischbach is getting an interactive special this fall, "A Heist with Markplier," in which fans can control his decisions during a museum heist. 

The decision to center more original programming on the site's already-popular creators is largely due to numbers, Kyncl explained. In the past three years, the number of channels with more than 1 billion views has grown 400%. The site also has 2 billion active users, 200 million of which come to YouTube daily just to watch gaming videos. 

"This creator-led momentum continues to grow," Kyncl said. "They're driving record audiences to YouTube and the numbers are astonishing."

Returning shows include "Cobra Kai," the site's breakout comedic drama, which is based on "The Karate Kid" films and will premiere its third season next year. (The first two seasons will be made available to everyone with ads beginning this fall as part of the shift to a free model). Season 3 of "Kevin Hart: What the Fit," in which he does outrageous workouts with fellow celebrities, is also coming in 2020.