Rupert Murdoch is stepping down at Fox and News Corp. What ...

The media world is reeling from the news Rupert Murdoch is retiring after decades building his empire. 

He's grown his businesses to include many of Australia's big daily newspapers, Britain's best-selling tabloids, and influential American outlets like Fox News.

In some ways it's no huge shock, given Mr Murdoch is 92 and has been gradually handing power to his son for some time.

But it's a momentous media moment – Mr Murdoch has been wielding influence in the press and politics since inheriting a newspaper in Adelaide in the early 1950s.

He's had remarkable business success, but has also been criticised over episodes such as the UK phone-hacking scandal and Fox News’s role in promoting rigged-election conspiracies, which led to Fox paying $US788 million to voting-machine company Dominion Voting Systems.

Former prime ministers Kevin Rudd and Malcolm Turnbull are among those who've previously called for a Murdoch Royal Commission to investigate how News Corp wields its power in Australia.

Rupert Murdoch is stepping down, but not stepping away.

From November, he'll be News Corp and Fox's Chairman Emeritus – a title given to a past chairman who remains associated with the business.

His eldest son Lachlan will become the sole chair of News Corp and continue to head up Fox.

Rupert Murdoch and his son Lachlan share similar views.(Reuters: Mike Blake)

In a letter to his staff, Rupert Murdoch said he would "be involved every day in the contest of ideas".

"Our companies are communities, and I will be an active member of our community," he wrote.

NPR journalist David Folkenflik, who documented Rupert Murdoch's rise in the book Murdoch's World, says the retirement isn't completely unexpected. Rupert Murdoch is well past retirement age, and he's been grooming his son for several years.

"One can understand why a 92-year-old billionaire might finally step away and leave things in the hands of his designated successor," Folkenflik says.

"But … it does take you aback. It's a moment to reflect. It's a moment to register all that he has done, his incredible successes, his extraordinary record and, you know, the wreckage he left in his wake as well."

Lachlan Murdoch is close to his father, and Rupert Murdoch's letter to staff outlines a shared worldview:

"My father firmly believed in freedom, and Lachlan is absolutely committed to the cause. Self-serving bureaucracies are seeking to silence those who would question their provenance and purpose. Elites have open contempt for those who are not members of their rarefied class. Most of the media is in cahoots with those elites, peddling political narratives rather than pursuing the truth."

It's reflective of how heading up a media empire is about much more than money to the Murdochs.

Bristol University media historian Simon Potter says the men appear to be driven by similar motivators.

"What really appealed to Rupert Murdoch was the sort of political power that owning a big media concern gave him – really the joy of doing the deal and being in the room where it happens," he says.

"And I suspect it's something that really appeals to Lachlan as well."

NPR's David Folkenflik says Lachlan Murdoch has some of his father's charm and is well-liked by his colleagues. But, he says, "he is not the same driving, ceaseless force that his father was in creating something from the Adelaide News to this enormous empire".

"It's just very hard to imagine a world in which Lachlan is seen as anything but a manager of properties rather than assembler of power and influence in the same way."

While some observers say a major shift is unlikely in the short term, there are differences between father and son that could prove consequential.

Some are simply generational. Rupert Murdoch maintains a passion for newspapers even as their social relevance and commercial value fades.

"Rupert Murdoch is maybe the last of the press barons who is really a newspaperman," Simon Potter says.

"And I think what you've seen in the Murdoch media empire is that newspapers have kept that privileged place probably for longer than they would naturally have done."

Professor Potter says one big question is how Lachlan Murdoch will navigate a "post-print future".

Lachlan Murdoch is seen as more politically conservative than his father in many ways, and some watchers expect outlets like Fox News could lurch further to the right.

"I think what we'll probably see is the Murdoch outlets double down on the sort of hardcore, radical, nationalist content that they've been engaged in for the last several years," says Matt Gertz, a senior fellow at the progressive industry watchdog Media Matters for America.

"The book on Lachlan Murdoch is that he is a true believer — that whereas Rupert Murdoch is willing to make common cause with far-right radicals, Lachlan really believes the things that they say."