Boyfriend caught in selfie mistake which exposed his cheating

The reflection showed a woman putting her legs on the dash. Photo / TikTok

A woman managed to expose her boyfriend's cheating antics through a selfie he sent of himself posing in a car.

Sydney Kinsch took to TikTok to reveal the moment she busted her partner of four years being unfaithful.

In the video, which has been viewed more than 1.4 million times, it shows a photo of her boyfriend wearing a pair of black sunnies as he looks directly into the camera.

While it appears to be innocent at first glance, upon further inspection, Sydney points out that there is actually another person sitting in the passenger seat beside him.

It shows a woman with her bare legs and feet up on the dashboard.

"Check the reflection in your boyfriend's sunnies ladies," Sydney captioned the post.

When she called him out on it, Sydney said he called her "crazy", but one week after he sent the photo, it was revealed he had been cheating on her for a month.

"I called him and asked if he realised he sent me a b**ch in his Snapchat and he had no idea," Sydney wrote in the comments section of her video.

"So I sent it to him and he called me crazy and that it was our friend's gf and that's he's allowed to have friends.

TikTok user Sydney revealed the detail in this selfie that alerted her to her boyfriend's cheating. Photo / TikTok

"He was with 'like 5 people'....I found out a week later ALL the details."

Sydney said after they broke up he "had the nerve to say to me 'I was throwing away 4 years'."

Her post has since been bombarded with hundreds of comments from equally shocked TikTok users.

"It's blowing my mind that he didn't notice," one woman wrote.

"Allowed to have friends?? Homegirl kicked her feet up on the dash, she definitely ain't (sic) just a friend. U dodged a bullet girl," added a man.

"What the f**k what kind of low life does that," a third person said.

Others revealed how they caught their partners cheating on them in a similar, if not the exact way.

"Literally how I caught my ex too lmao," one woman said.

"Omg girl! Same! He is now my ex husband, but legit the same type of photo," a second woman wrote.

"Mine sent me a video of him making out with another chick at a concert I got him tickets for," added a third.

Meanwhile, last year Jane Slater, an NFL sports reporter in the US, revealed how she busted her now-ex boyfriend by his FitBit device.

The pair linked their FitBits, and for a while all was well as they "motivated" each other to keep on track.

But being able to monitor her partner's movements meant Slater was able to catch him out when she noticed something suspicious about his increased energy levels.

In a Twitter conversation with fellow NFL reporter Albert Breer, where the pair discussed exercise gifts, Slater wrote about her FitBit: "Didn't hate it until he was unaccounted for at 4am and his physical activity levels were spiking on the app.

"Wish the story wasn't real," she posted.

She had also revealed a time when she was dating a guy who came home drunk with another girl, forgetting she was spending the night.