Robin*, 24, and her boyfriend were having pizza before a concert when all of a sudden, her phone pinged. It was a notification from Snapchat, alerting her that she had received a snap. It was an image from her ex-boyfriend, his abs plastered on her phone's screen. The caption: "Want to play?"

Robin attempted to explain to her boyfriend that she had no idea why her ex would send her such an explicit photo on Snapchat. But as she later confided to Mic, that was a massive lie. Robin and her ex-boyfriend had been exchanging steamy snaps for the past four months, after they broke up over a career move that placed him in a different city.

Although Robin suspected she might one day get caught, "there always seemed [to be a level of] deniability," she told Mic. "I could always just say he is sending them to me unprompted."

But even though Robin's boyfriend wasn't happy, she didn't feel like what she was doing counted as cheating — and even if it was, she reasoned, there wouldn't be any evidence of it. Because Snapchat is an ephemeral messaging app, pictures can be sent back and forth between partners with a timer set, eventually theoretically fading into the ether after an allotted time frame. The app provides people like Robin with the ideal platform to engage in digital flirtation.

"It always seemed so harmless," Robin told Mic of sexting with her ex. After all, "we aren't having actual sex."

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Sexting without strings: With nearly 100 million monthly active users, Snapchat is clearly not exclusively used by women like Robin looking to receive some nude selfies on the side. In fact, according to a 2014 study conducted by the University of Washington, only 14% of the Snapchat users polled reported sending sexy images from the app. Yet because Snapchat is an ephemeral messaging app, it's the perfect vehicle for people who want to derive sexual satisfaction outside their own relationships without getting caught.

Another benefit to using Snapchat stems from the allure of "secret" communication with people your partner is not aware of. While social media apps like Instagram and Facebook rely on public interaction, Snapchat operates solely behind a curtain. For people who use it as a way to get off with other people, they equate it to looking at porn to masturbate. They're looking, but not touching, and therefore they deem it acceptable. In fact, according to a 2015 study published in the journal Cyberpsychology, Behavior, and Social Networking found that while more people use social networks like Facebook for innocuous reasons like keeping in touch with friends, Snapchat was more often used for flirting and meeting new partners, which often prompted jealousy in romantic relationships.

"The only reason I can think of is that she really does have something to hide."

On Reddit, there are numerous threads by users who have recently discovered their partners are talking to former flames or sending sexy pictures via Snapchat. Posters come to Reddit asking if they're paranoid, or if they're losing their minds. The element of secrecy provided by Snapchat allows their imaginations to run wild.

"What does this say? Am I paranoid?," one redditor wrote after seeing a guy who was known as a "womanizer" was on his girlfriend's best friends list. "Should I confront her on it? How?"

"Why would she use Snapchat?," another asked after discovering that his girlfriend had received a snap from someone she'd previously slept with. "The only reason I can think of is that she really does have something to hide."

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Is it cheating, or is it something else?: Obviously, the idea of using a digital platform to blur the lines of fidelity is nothing new; from joining websites like Ashley Madison to having cybersex in the early days of AOL chatrooms, people have been using technology to get some strange on the side for years. Yet Snapchat is somewhat unique in its ephemerality, as well as the fact that it provides an instant, customizable masturbatory experience for users.

Most of the people Mic spoke with said they sent Snapchat nudes for the same reason they enjoyed watching amateur porn on XTube: because they enjoyed the sense of power and agency from asking for and receiving specific types of NSFW content in real time. The fact that sexting with someone on Snapchat allows you to customize your content is an added bonus.

"You feel more involved with the experience because you know they're sending you back sexy snaps as they're actually doing it," Aaron, 25, said.

A computer programmer living in Hollywood, Aaron has been sending and receiving risque snaps since the app first came out in 2011, regardless of whether or not he's been in a relationship at the time. His sexting partners are primarily mutual friends he's messaged on Facebook and people he used to attend college with. He said he continued to send snaps to strangers when he started dating his current girlfriend because he is able to compartmentalize his relationship and rubbing one out with an old classmate on Snapchat.

"It's like ordering fast food, you know? You want to see a girl's breasts from a certain angle, so you ask," he told Mic. "You both get to see exactly what you want. To me that's hot."

Ethan, a 21-year-old gay man living in Hollywood, echoed this sentiment. "For me it is basically like watching custom porn. I'm getting to see someone get off in real time with me," he told Mic. For both of these men, amateur porn doesn't have the same voyeuristic draw that Snapchat offers them.

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A harmless form of validation: Although both Ethan and Aaron are in committed relationships, they don't see an issue with sending photos back and forth to other people. To them, sending nudes on Snapchat is harmless, a way to remind themselves that they're still attractive to other people.

Robin said that when her boyfriend caught her sexting her ex, she explained that he continued to send her photos because he felt insecure about his body. She told Mic that she sends them back because "sometimes I like to be reminded that he still finds me sexy."

But while they might tell themselves it's not a big deal to snap the occasional topless photo to an ex, to a degree, people who use Snapchat in a relationship know that they're crossing the line — which is why they don't tell their partners about it in the first place.

"I don't think I'd be happy with my boyfriend finding out I was sending topless photos to another guy, but I also weirdly justify it with: At least it's just pictures? I don't know," Robin told Mic.

Aaron agreed, saying that he doesn't consider what he was doing on Snapchat a form of "cheating" — even though he acknowledged he would definitely be in a bad position if his significant other found out. "It isn't like I meet any of these women," Aaron explained. "It's just like, a way to have some sexy conversations with that girl in your bio class you never asked out in college ... I could be doing worse."

Ethan agreed, saying that Snapchat provided a sexual outlet that helps him stay physically faithful to his partner. "I would rather jerk off with another guy than go out and blow someone," he said, laughing.

"If you feel like you may be bending the rules, then you probably are."

The true cost of cheating: For anyone with a wandering eye, or a penchant for flirtation, Snapchat seems like a harmless way to explore. But like anyone who is flirting with unfaithfulness, Aaron and the rest are adept at rationalizing it.

"It's really simple," Ken Page, psychotherapist and author of the book Deeper Dating: How to Drop the Games of Seduction and Discover the Power of Intimacy, previously told Mic. "If you feel like you may be bending the rules, then you probably are ... That means that you're doing something that is damaging the trust in the relationship."

While that might be true, all of the people Mic spoke with affirmed that they had no plans to actually meet the individuals they were sexting. For them, the appeal was purely carnal, totally separate from their actual, IRL sex lives. They were able to justify sending sexy pictures to their sexy friends without feeling like they were crossing any boundaries.

Like any discourse on infidelity, whether or not sexting on Snapchat counts as cheating is not cut and dry: While some might consider it the ultimate form of betrayal, other partners might not be bothered by it at all. The answer to that question largely varies depending on the couple. That said, it is important to remember that unlike the 10-second photos people send back and forth to each other, the fallout from a hastily sent snap can potentially last for much longer.

*First names have been used to allow subjects to speak freely about private matters.