SAN FRANCISCO • The co-founders of Google are stepping down as executives of its parent company, Alphabet, ending a remarkable two decades during which Mr Larry Page and Mr Sergey Brin shaped a start-up born in a Silicon Valley garage into one of the world's largest, most powerful - and, increasingly, most feared - firms in the world.

Mr Sundar Pichai, who has been leading Google as chief executive for more than four years, will take on additional duties as Alphabet's CEO, the position held by Mr Page.

The company is not filling Mr Brin's position as president.

Mr Brin and Mr Page met as Stanford University graduate students in 1995 and started the company three years later. What started as a way to catalogue the growing Internet has now become one of the most powerful companies in the world.

Google dominates online search and digital advertising and makes the world's most widely used operating system for smartphones, Android. Its services range from online tools to e-mail, cloud computing systems, phones and smart speaker hardware.

Mr Page and Mr Brin, in announcing the news on Tuesday, said the firm has "evolved and matured" in the two decades since its founding.

Both promised to stay active as board members and shareholders.

"Today, in 2019, if the company was a person, it would be a young adult of 21 and it would be time to leave the roost," they wrote in a blog post.

Alphabet - an umbrella corporation that the two created in 2015 - still boasts Google as its central fixture and key moneymaker. But it is also made up of what are known as "other bets", or long shot projects. That includes drone company Wing and self-driving car firm Waymo.

Mr Page and Mr Brin have been noticeably absent from Google events in the past year.

Both stopped making appearances at the weekly question-and-answer sessions with employees, and Mr Page did not attend this summer's Alphabet shareholders' meeting even though he was still in the CEO role.

Alphabet has been positioning Mr Pichai as the de facto leader for quite some time.

Mr Pichai, 47, has worked at the company for 15 years, serving as a leader in projects to build the company's Chrome browser and overseeing Android.

Mr Pichai, who has an engineering background, took over as the head of Google's products before being promoted to CEO when Alphabet was created. He is known as a soft-spoken and respected manager.

Long-time tech analyst Tim Bajarin of Creative Strategies said that for all intents and purposes, Mr Pichai has been the public face and the most instrumental person inside Google for the past few years.

Alphabet has made him the top executive voice at shareholders' meetings, on earnings call and as a spokesman at congressional hearings. So far, the company has shown no signs that it intends to replace Mr Pichai at Google.

But Mr Bajarin said doing so might make sense, given that Mr Pichai will have so much on his plate as CEO of the overall business, including regulatory pressures from the United States and Europe.

Google is facing strong pushback from privacy groups, which are concerned about the personal information that it has collected on its users, mostly to target advertising.

The firm also faces complaints that it abuses its dominance in search and online advertising to push out rivals.

Google is the subject of antitrust inquiries from the US Congress, the US Department of Justice and European authorities, among others.

The company has also faced harsh criticism about the material on its sites - and was slapped with a US$170 million (S$231.8 million) fine because its video streaming site YouTube improperly collected personal data on children without their parents' consent.

In the short term, Mr Bajarin does not expect much to change at the company.

And if anything does, it will be due to government regulation - not the executive shuffle.

As for Mr Page and Mr Brin, Mr Bajarin said: "Keep in mind, they are not losing their title as billionaires, but they are changing their roles."

Mr Brin and Mr Page still hold more than 50 per cent of voting shares in Alphabet.

Google has nearly doubled its headcount since Mr Pichai took over as chief executive, growing from a company of 59,000 employees to 114,000.

ASSOCIATED PRESS