To those fearful of a future in which videos of real people are indistinguishable from computer-generated forgeries, two recent developments that attracted an audience of millions might have seemed alarming.

First, a visual effects artist worked with a Tom Cruise impersonator to create startlingly accurate videos imitating the actor. The videos, created with the help of machine-learning techniques and known as deepfakes, gained millions of views on TikTok, Twitter and other social networks in late February.

Then, days later, MyHeritage, a genealogy website best known for its role in tracking down the identity of the Golden State Killer, offered a tool to digitally animate old photographs of loved ones, creating a short, looping video in which people can be seen moving their heads and even smiling. More than 26 million images had been animated using the tool, called Deep Nostalgia, as of Monday, the company said.

The videos renewed attention to the potential of synthetic media, which could lead to significant improvements in the advertising and entertainment industries. But the technology could also be used — and has been — to raise doubts about legitimate videos and to insert people, including children, into pornographic images.

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The technology could also have a destabilizing effect on global affairs, as politicians claim that videos, including genuine ones, are fake in order to gain an advantage that the law professors Robert Chesney and Danielle Citron have called the “liar’s dividend.”

In Gabon, opposition leaders argued that a video of President Ali Bongo Ondimba giving a New Year’s address in 2019 was faked in an attempt to cover up health problems. Last year, a Republican candidate for a House seat in the St. Louis area claimed that the video of George Floyd’s death in police custody had been digitally staged.

As the technology advances, it will be used more broadly, according to Mr. Gregory, the artificial intelligence expert, but its effects are already pronounced.

“People are always trying to think about the perfect deepfake when that isn’t necessary for the harmful or beneficial uses,” he said.