In his hacking lawsuit being heard in a British court, Prince Harry aims to land another blow against a tabloid industry that has long been accused of widespread privacy abuses but that has been forced in recent years to rein in its excesses.

So even if Harry, the younger son of King Charles III, wins his suit against the Mirror Group Newspapers for allegedly hacking his cellphone more than a decade ago, analysts question how much of an impact a legal victory would have on publications that have already had to adapt because of hefty legal settlements, prison time for their journalists and the threat of regulation.

The prince, who took the stand on Tuesday, has been at war with the raucous, freewheeling press for years. And since Britain’s phone-hacking scandal broke, it has forced a News Corporation publication to close, helped send several prominent journalists to jail, reaped hundreds of millions of pounds in legal fees and compensation for victims, and led Parliament to seriously consider regulating the industry.

At the same time, the once-mighty British tabloids have been weakened by a digital revolution that has transformed the global media landscape by gutting revenue, even as the public’s appetite for celebrity news has not waned.

“Things have moved — they haven’t necessarily got better in every way, but they have definitely moved on,” said David Yelland, a former editor of The Sun and founder of Kitchen Table Partners, a communications company. “Tabloid journalism doesn’t exist in the form it did.”

Mr. Yelland said it was not that “there is no invasion of privacy now — there is, particularly around the use of images taken from social media.” But he added that problematic media content is now more likely to emerge from commentary than material recovered from someone’s garbage cans or by paying investigators to get access to celebrities’ bank statements.

Lawyers for Harry, also known as the Duke of Sussex, accuse the Mirror Group Newspapers of using private investigators to illegally gather information on him for stories prominently featured from 1996 to 2011. They say the private eyes took part in voice-mail interception and employed photographers who used unlawful means to find out the whereabouts of Harry and his associates.

Harry is one of four plaintiffs, including two actors who appeared in the popular British television series “Coronation Street.” The case is focused on charges that the papers hacked Harry’s cellphone, as well as those of his brother, Prince William; aides; and a former girlfriend throughout the early 2000s.

Andrew Green, the lead lawyer for the Mirror Group, argued in court on Monday “that there is simply no evidence that the Duke of Sussex was ever hacked.”

Phone hacking, intercepting voice-mail messages without permission, is illegal in Britain. But in the first decade of this century, there were widespread abuses by the tabloid media, including obtaining private information such as phone bills or medical records by deception, known as “blagging.”

The royals were prime targets, and in 2006-7, the royal editor of The News of the World, Clive Goodman, and a private investigator, Glenn Mulcaire, were convicted of intercepting royal aides’ voice-mail messages.

Prof. Timothy Luckhurst, principal of South College at Durham University and the founding head of the center for journalism at the University of Kent, said the pivotal change in media came after the startling revelation that The News of the World, a Rupert Murdoch newspaper, had hacked the phone of a missing child, Milly Dowler, who was later found slain.

The case spurred an inquiry that was named for the judge who led it, Brian Leveson, and in 2011 resulted in News Corporation’s closing of the 168-year-old newspaper.

“The Leveson inquiry involved really intense scrutiny of and profound criticism of elements of the popular press in the U.K., and it led to recommendations that, had they been accepted, would have led to the first state involvement in the regulation of the press in the U.K. since the abolition of press licensing in the 17th century,” Professor Luckhurst said.

Britain’s policymakers had long struggled with how to curb the tabloids’ excesses.

But the idea that Parliament would regulate the very people whose job it was to hold lawmakers to account proved a big enough threat that it acted as a form of constraint on journalists. The regulation idea was ultimately rejected amid wariness about trampling on press freedom, Professor Luckhurst said, “but the press understood, at that time, that self-regulation was going to have to deliver substantial improvements in conduct if it was going to endure.”

“What Prince Harry is doing by appearing in court against Mirror Group Newspapers,” he added, “is essentially to dredge up behavior which was largely conducted — if at all — before the Leveson inquiry had its impact.”

Perhaps the most graphic example of phone hacking was the case of Andy Coulson, a former editor of The News of the World, who quit in 2007 to become a Downing Street adviser to Prime Minister David Cameron. After the hacking case resurfaced in 2011, Mr. Coulson ended up not only losing that job, but also was jailed for his role in the scandal.

Mr. Murdoch’s empire was reported to have paid a total of more than 1 billion pounds in legal and other fees as well as compensation to victims of journalistic malpractice. According to a recent court filing by Harry, Prince William was among those who accepted a significant payment to avoid going to court.

British tabloids have since modified their approach rather than retreated, still serving up celebrity news and gossip but without overtly breaking the law.

In recent days, for example, the news media has been dominated by coverage of the resignation of the former television host Phillip Schofield, who has admitted lying about a relationship with a younger, male colleague while he was married.

“The fact that these stories emerge by patently legal means and are reported through interview and conversation with people who are genuine sources is a change in terms of conduct, but it doesn’t suggest that there has been any change in tastes of the British public,” Professor Luckhurst said.

Social media has proved to be a valuable resource for journalists to carry on chasing celebrity news. Mr. Yelland, the former editor of The Sun, said that many tabloid journalists devote hours to scrolling through the accounts of anyone connected to the rich and famous to pounce on an ill-advised Facebook or Twitter post.

Some critics say that despite a shift in tactics, the tabloids are still unaccountable and as powerful as ever — and they want tougher measures put in place.

“What they may have lost in print circulation they have made up for in social media clout and influence over politicians,” said Brian Cathcart, a former director of Hacked Off, a group that campaigns for press accountability.

“They animate and direct the mob day by day and hour by hour,” he said, “making rational politics impossible but always serving the interests of their cynical and cruel owners.”

Yet for Prince Harry, a legal victory is as likely to stoke his feud with the British tabloids as to end it, experts say.

“If you continually go for them, then they will go for you,” Mr. Yelland said. “The problem with the British press for Harry and Meghan is not invasion of privacy; it’s comment, it’s the way their coverage is configured.

“And if you have a generation of editors that hate them, they can do what they like on a day-to-day basis — even if Harry and Meghan win the case.”