Yet, few companies lent any support to the commission at its news conference; Viacom and Disney sent representatives, but other companies were absent.

“What we’ve got here is an expansion of Coppa that some in the industry would say has gone too far,” said Alan Friel, a lawyer who leads the media and technology practice at the firm of Edwards Wildman Palmer. “But the F.T.C. has provided exceptions that continue to allow internal use of a child’s data, including one-time use of contact information for facilitating promotions and send-a-friend e-mails.”

In an era of widespread photo sharing, video chatting and location-based apps, the revised children’s privacy rule makes clear that companies must obtain parental consent before collecting certain details that could be used to identify, contact or locate a child. These include photos, video and audio as well as the location of a child’s mobile device.

While the new rule strengthens such safeguards, it could also disrupt online advertising. Web sites and online advertising networks often use persistent identification systems — like a cookie in a person’s browser, the unique serial number on a mobile phone, or the I.P. address of a computer — to collect information about a user’s online activities and tailor ads for that person.

The new rule expands the definition of personal information to include persistent IDs if they are used to show a child behavior-based ads. It also requires third parties like ad networks and social networks that know they are operating on children’s sites to notify and obtain consent from parents before collecting such personal information. And it makes children’s sites responsible for notifying parents about data collection by third parties integrated into their services.

Collecting data to show children contextual ads based on the content of a site or app, however, will not require parental consent. “The only limit we place is on behavioral advertising,” Mr. Leibowitz said. “Until and unless you get parental consent, you may not track children to create massive profiles” for behavior-based ads.