The YouTube CEO and one of the first Google employees, Susan Wojcicki, is stepping down from her role at the tech giant that started in her garage nearly 25 years ago, she said in a personal update on the video-sharing platform on Thursday.

Wojcicki, 54, will be replaced by her deputy Neal Mohan, a senior advertising and product executive who joined Google in 2008.

The change of guard comes as YouTube’s advertising revenue fell for the second straight quarter amid intense competition for viewing time with short-form video services such as TikTok and Facebook’s Reels, and streaming services like Netflix.

Mohan, a Stanford graduate, was appointed chief product officer at YouTube in 2015. He focused on building YouTube Shorts, Music and subscription offerings in the role.

He previously spent nearly six years at DoubleClick, a company Google acquired in 2008, and later served for about eight years as senior vice president of display and video advertising at Google.

One of the most prominent women in tech, Wojcicki said she will focus on “family, health, and personal projects”, and plans to take on an advisory role at Alphabet.

She was previously senior vice president for ad products at Google and became the CEO of YouTube in 2014.

Read: YouTube takes aim at TikTok

“It strikes me as a forced exit caused by YouTube’s underperformance in recent quarters… What’s less clear is whether Mohan, who’s had a relatively low profile to date, has the leadership qualities to get YouTube back on track,” said Paul Verna, analyst at Insider Intelligence.