YouTube has already invested in original programming for its subscription-only YouTube Red service. Now the video giant is going to launch original series — with celebrities and some of YouTube’s biggest creators — on the free, ad-supported side of the service.

YouTube announced six new shows, which will be exclusively available on YouTube, at its Brandcast event Thursday in New York for marketers. New original series come from Kevin Hart, Ellen DeGeneres, singer Demi Lovato, YouTube comedy duo Rhett & Link (of talk show “Good Mythical Morning”), Ryan Seacrest, and YouTube’s the Slow Mo Guys.

Singer Katy Perry appeared on stage to announce that she will be part of the “Best.Cover.Ever” singing competition show from Seacrest and Endemol Shine North America, which also will feature Lovato, Backstreet Boys, Jason Derulo and Charlie Puth. In addition, Perry will be featured in a YouTube-exclusive “Katy Perry Live Special,” in which she will host a live album listen-along for fans.

“Why now, after all these years, do we feel the time is right for ad-supported originals?” YouTube chief business officer Robert Kyncl said at the event. “Frankly, because they’re becoming more and more rare.”

James Corden, host of CBS’s “The Late Late Show,” credited YouTube with the surging popularity of his show. The “Late Late” YouTube channel was the fastest to reach 10 million subscribers (it currently has nearly 10.3 million) and has generated 2.8 billion views to date. And Corden noted that his “Carpool Karaoke” segment with Adele was the most-viral video on YouTube of 2016. Corden also performed “YouTube: The Musical,” paying homage to the notable personalities on the platform.

“I realized I didn’t have to make a show for any time slot because we had the internet — and more than that, we had YouTube,” Corden said.

YouTube CEO Susan Wojcicki told the Brandcast audience that YouTube is something even larger than TV, spanning the world and providing interactive features that enable fans to more deeply connect with their favorite content creators.

“The platforms for the future are different from the ones of the past,” Wojcicki said in her intro. “YouTube is not TV — and never will be.” That sounded odd, considering it just launched YouTube TV with more than 40 live broadcast and cable channels last month in five markets (not to mention the fact that it used the event to announce the expansion into ad-supported, TV-style original series). But her point was that YouTube encompasses a significantly vaster diversity of viewpoints and community engagement than traditional television.

Still, Wojcicki made a direct comparison to television, claiming that more people 18-49 visit YouTube on mobile devices alone than any broadcast or cable TV network during primetime. (At last year’s Brandcast event, YouTube said it reached more viewers in the 18-49 demo than the top 10 primetime shows.)

Wojcicki also directly addressed the recent controversy that has beset YouTube, over ads appearing in extremist videos. The issue prompted dozens of brands to pull spending from the site. “We apologize for letting some of you now,” the CEO said. “I’m here to say we can, and will, do better.”

Here’s a rundown of YouTube’s newly announced original ad-supported shows:

“Ellen’s Show Me More Show”: Twice-weekly series will include original content with exclusive access to the talk-show host’s favorite moments and celebrity guests, and behind-the-scenes glimpses.

Twice-weekly series will include original content with exclusive access to the talk-show host’s favorite moments and celebrity guests, and behind-the-scenes glimpses. “I Am: Demi Lovato”: Grammy-nominated artist documents the writing and recording of her newest album, as well as performances around the world; slated to premiere in the fall.

Grammy-nominated artist documents the writing and recording of her newest album, as well as performances around the world; slated to premiere in the fall. “Kevin Hart: What the Fit?”: Comedy superstar will team up with celebrity friends and YouTube stars each week they attempt to master a different grueling (and sometimes ridiculous) workout routine. Produced in collaboration with Lionsgate, the show will appear on Hart’s Laugh Out Loud channel on YouTube.

Comedy superstar will team up with celebrity friends and YouTube stars each week they attempt to master a different grueling (and sometimes ridiculous) workout routine. Produced in collaboration with Lionsgate, the show will appear on Hart’s Laugh Out Loud channel on YouTube. “Good Mythical Morning”: Rhett & Link will produce a long-form expansion of their daily talk show to give fans “larger-than-life stunts, star-studded celebrity guests, in-depth segments, zanier challenges, field correspondents and over-the-top laughs,” according to YouTube.

Rhett & Link will produce a long-form expansion of their daily talk show to give fans “larger-than-life stunts, star-studded celebrity guests, in-depth segments, zanier challenges, field correspondents and over-the-top laughs,” according to YouTube. “The Super Slow Show”: YouTube’s the Slow Mo Guys will explore everything from the tiniest phenomena to the biggest spectacles — all shot in slow motion.

YouTube held the Brandcast event (as it did last year) at the Jacob K. Javits Convention Center in Manhattan, with a crowd of about 2,800 YouTube creators, ad execs and others — making it the biggest of the IAB’s Digital Content NewFronts events.

Following the main show, Perry was scheduled to return to the Javits stage out to perform a set including “Dark Horse,” “Teenage Dream” and “Firework,” and new songs “Chained to the Rhythm” and “Bon Appetit.”

Pictured above (l. to r.): Kevin Hart, Ellen DeGeneres, Katy Perry