If there's one lesson out there that applies to all relationships, it is that the truth will come out eventually.

And if you need more proof of this, then check out the story of 24-year-old TikTok user Sydney Kinsch, who recently took to the social media platform to reveal how she discovered her ex-boyfriend was cheating on her.

After being sent a seemingly-innocent Snapchat by her then-boyfriend, Sydney noticed a tell-tale reflection in his sunglasses.

Sydney captioned her post: "check the reflection in your boyfriend’s sunnies ladies. [sic]"

Take a look at the TikTok video in question below: 

[[tiktokwidget||https://www.tiktok.com/@sydneykinsch/video/6890397554001988869]]

She also wrote over the video: "That one time my boyfriend of 4 years snapchatted me him cheating on me [sic]".

Upon a closer inspection of the image, Sydney saw something very shocking indeed. That's because there, reflected in the lens of his shades on the passenger seat, was another woman wearing shorts and stretching her feet out of the car's window.

Needless to say, a number of people enjoyed the video, and in just six days, the post has been viewed over 2.2 million times.

And many Tiktokers took to the comments section of Syndey's post to slate her cheating man:

For instance, one TikTok user wrote: "Everything always comes out one way or the other." Meanwhile, another sympathetic person added: "What's done in the dark comes out in the reflection of your sunglasses!"

And it seems like this is a rather common way to catch cheating partners, as one commenter wrote: "How I caught my ex too. Reflection in a window."

And another TikTok user chimed in: "This legit happened to me!!! My ex took a selfie to send me and I saw a chic in his glasses reflection lol [sic]"

Another quipped: "Don't know why he's got the sunnies on, he's not that bright."

So the next time your partner sends you an innocent-looking selfie, you may want to check out the surrounding reflections.

Cheating is one of the worst things you can do to your significant other. Being an extreme breach of trust, infidelity can destroy once happy relationships and put years of love, memories and effort to waste. And in many cases, it's not something that can be forgiven.

I mean, there's no "good" excuse for locking lips, or more, with someone who's not your partner (no matter how many vodka sodas you consumed prior to the fact). It's all about self-control, and if you're really finding it that difficult to restrain yourself from pouncing on anything that moves, it's probably time to re-evaluate your priorities, and your relationship.

Luckily, this era of modern technology has made the lives of cheaters much more difficult. Case in point: a man who saw his girlfriend cheating on him at a party got even by taking a selfie with the pair while they were going for it.

20-year-old Mariano, from Quilmes in Bueno Aires had gone for a night out without his girlfriend, but realised that they were both at the same party when he saw her kissing another man.

Exercising serious restraint, Mariano saw his girlfriend cuddling up to the unidentified man and instead of hashing it out then and there, took a selfie to commemorate the occasion.

The ensuing photograph sees Mariano's significant other exchanging tongue with the other guy, while he poses for the camera like it's no big deal.

"My girlfriend (now ex) didn't realise that we came to the same party," he captioned the picture.
[[twitterwidget||https://twitter.com/Marian0Nicolas/status/970737338916753413]]

Clearly, the 20-year-old's girlfriend wasn't aware that she'd been caught being unfaithful until her now ex-boyfriend uploaded the photograph to Twitter.

And it didn't just end there. After her infidelity went viral, garnering over 67,000 likes on Twitter, Mariano followed up his initial tweet with a screenshot of his ex-girlfriend trying to explain herself.

"I was very drunk and the fatty was very insistent with me, he told me loads of things and I do not know how it came to that," she stated in a rather body shame-y manner. "I seriously love you and I want to be with you."

After reading her long-winded excuses, Mariano simply replied "You could have made a bit more of an effort," and followed it up with the laughing-crying emoji.

"Thank you girls for all your support photos, and thanks to all the soldiers for their memes, always in my heart" he later posted on Twitter.

[[twitterwidget||https://twitter.com/Marian0Nicolas/status/970605229673676800]]

As could be expected, the couple have now split up.

While it's never nice to find out that your significant other is cheating on you, I think we can all agree that in Mariano's case it's better that he found out sooner rather than later. I mean, if you're going to cheat, at least make sure you check the guest-list first...

In related news, here are 12 things all men should do to make women feel more comfortable on dates.

A woman has taken to TikTok to show her followers how her cheating boyfriend accidentally exposed his own affair in a selfie he sent of himself.

Sydney Kinsch had been with her boyfriend for four years before an interesting Snapchat pic forced the cat of out the bag.

The video, which currently has more than 1.7 million views at the time of writing, features a picture of her boyfriend wearing a pair of black sunglasses, looking directly into the camera.

[[tiktokwidget||https://www.tiktok.com/@sydneykinsch/video/6890397554001988869]]

It may initially appear to be an ordinary car selfie, however, if you look closer you can see that he isn't the only person in the car. Indeed, there is another person sitting in the passenger's seat right next to him.

This other person is a woman with her bare legs and feet up on the dashboard.

"Check the reflection in your boyfriend’s sunnies ladies," Sydney captioned the TikTok video.

Sydney later called her boyfriend out on what she instinctively felt was an affair. According to her, he responded by calling her "crazy", however, a week after the photo was sent, she found out that he had been cheating on her for an entire month.

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

"So I sent it to him and he called me crazy and that it was our friends gf [sic] and that’s he’s allowed to have friends. He was with 'like 5 people' ... I found out a week later ALL the details."

Needless to say, the post has been inundated with comments by appalled TikTok users, with one writing: "Don't know why he's got the sunnies on, he's not that bright."

Another took to the comments to share: "This legit happened to me!!! My ex took a selfie to send me and I saw the [chick] in his glasses reflection lol. He was at a restaurant lol."

1. Mixed messages

2. It's a yard sale!

3. Bro's before ho's

4. Swipe left

5. Nice paint job

6. Say cheese!

7. Damn. Stay strong, Linnie

8. Honk, honk! (Should've written in bigger letters, though.)

 9. Awww, a card!

Uh-oh.

 10. Money well spent

 11. It's a treasure hunt!

 12. Game over

 13. Americans get revenge like this...

 14. ...and Brits get revenge like this.

 15. Sick sign!

 16. Pure evil

 17. I'm glad these two are going to work things out.

As technology becomes more advanced, it gets easier and easier to catch cheaters. But most people seem to prefer to take their revenge the old-fashioned way, making signs, spray-painting graffiti, or writing adorably spiteful notes. It's nice to see our society hasn't gone totally digital. Make sure you never cheat on someone good at arts and crafts - their sign publicly condemning you will be very legible and aesthetically pleasing.