Noted: Snapchat Without the Chat

Photos are shot and sent with the assurance that they will disappear automatically a few seconds after they’re viewed. No lingering blackmail material from bachelor parties or cellulite-exposing swimsuits.

In fact, since the images are fleeting, users are liberated to share the least flattering or most embarrassing “selfies”: lots of intentionally crossed eyes and double chins, lots of sitting on the toilet seat or throwing up on the Ferris wheel.

Until recently, Snapchat’s Guide for Parents prohibited children younger than 13 from using the app and required parental consent for anyone 13 to 17. But last week, the company introduced a PG version called SnapKidz that allows saving and captioning snapshots but not sending or receiving them. Of course, nobody is asked to produce a driver’s license, and in practice an overwhelming number of the 100 million photos shared every day are from teenagers and tweens — those too young to remember the provenance of the self-destructing reel-to-reel tape in “Mission: Impossible.”

“My brother, who’s 12, uses it with all his friends,” said Katya Stambler, a 15-year-old in Los Angeles, referring to traditional Snapchat. “They kind of doll themselves up for it, put on makeup. Older kids are less self-conscious. My friends and I take ugly pictures. You want to make the other person laugh, if only for three seconds.”

Proclamations from the creative team at Snapchat sound lofty and lyrical. The Web site states, “The allure of fleeting messages reminds us about the beauty of friendship — we don’t need a reason to stay in touch.”

Reality is somewhat different. “A lot of teens use it for sexting,” Katya said. “Parents are kind of against it. But as I explained to my mom, it’s like driving a car: you can either be safe or be reckless.”

Snapchat’s built-in disappearing act would seem to allay concern about images living in perpetuity on the Web, resurfacing just in time for law school applications or job interviews.

And yet. ... Anyone who’s quick, and determined to outwit the system, can take a screenshot of a photo before it evaporates. (Snapchat has always promised to send a notification when it detects an “illegal” screenshot, but the newest version of Apple’s iOS disables this function.) And a technically savvy Snapchatter (sound like any middle-schooler you know?) can overcome the limitations of the operating system on a mobile device, a feat known as “jailbreaking” on an iPhone or “rooting” on an Android.

“People who are pretty dumb can do it,” said Matthew Vincent, a 13-year-old in Austin, Tex., “and I’d say 90 percent of my class is using this app.”

“We don’t ever say that we’re a secure way to send ugly photos,” said Evan Spiegel, one of Snapchat’s founders. “We allow the Snapchat community to enforce its own norms. If you want to play a mean joke, we can’t stop you. But it’s important to look at how people build and maintain friendships. They would gain nothing in friendship by saving an ugly photo and posting it.”

Mr. Spiegel and Bobby Murphy conceived the application as students at Stanford. (There is a pending lawsuit from a former classmate who claims it was his idea, similar to the legal battle over Facebook; the blogerati have dubbed him Snapchat’s Winklevoss.) “It felt awful to be on social networks presenting myself as this awesome guy: ‘Here I am at the coolest party or on a great vacation,’ ” said Mr. Spiegel, now 22, “when a lot of time I’m in sweat pants watching a movie. People are hungry for things that are in the moment, authentic, not Photoshopped.”

Chew on that. And don’t worry about the spinach in your teeth.