A woman discovered that her boyfriend of four years cheated on her in the most 2020 of ways — by spotting a clue in a selfie. A video detailing the bizarre infidelity reveal currently boasts more than 1 million views.

“That one time my boyfriend of 4 years snapchatted me him cheating on me,” reads the description of the short clip shared on TikTok Saturday by one Sydney Kinsch.

The incriminating footage begins innocuously enough with Kinsch standing in front of a selfie of her alleged boyfriend, who is sporting sunglasses. Things take a turn, however, when she steps aside to reveal the reflection of a girl’s legs poking out of a car window in one of the lenses. The clip is aptly captioned “check the reflection in your boyfriend’s sunnies ladies.”

The videographer later described in the comment section how she brought the bombshell to her beau’s attention.

“I called him and asked if he realized he sent me a b – – ch in his Snapchat and he had no idea,” she wrote. “So I sent it to him and he called me crazy and that it was our friend’s gf and [that] he’s allowed to have friends.”

Kinsch said she discovered a week later that the sleazeball had been philandering for the past month with five different women.

Needless to say, the scorned woman’s detective skills garnered her more than 175,000 likes and oodles of sympathetic responses from the TikTok peanut gallery.

“Guys always thinking they can pull a fast one on us,” said one comment-section commiserator about Kinsch’s revelation.

“Don’t know why he’s got the sunnies on, he’s not that bright,” quipped one.

Another described a similar incident where she discovered her ex’s cheating ways through a reflection in a window.

In the creepier iteration of the above scenario, a Japanese stalker allegedly figured out where a female pop star lived based on the reflections of her pupils in her social-media pics.