Meeting women online and through dating apps can feel a bit dodgy in the day and age of "catfishing"—especially now that people have become surprisingly adept at altering how they look in photos. (Oh, the magic of lighting, good angles, and Photoshop.)

Still, there's a reason photo-based dating apps like Tinder are so popular: Humans like to judge whether or not we're attracted to someone at first glance, and that means people reveal a lot about themselves—even if they don't intend to—with their personal dating profile.

Of course that doesn't mean we're not immune to dating app traps. Those skimpy, night-on-the-town pics and the racy glamor shots you see? They're classic ways to catch guys hook, line, and sinker. 

But what do these pictures really tell you about her? We asked online dating expert Julie Spira to weigh in on what her sexy selfies and even sexier beach-bod shots reveal. And while we would never call these hard-and-fast rules—take them with a grain of salt, OK?—they're certainly useful guidelines for reading between the lines of her Tinder profile.

What it means if: She's selected a sexy selfie

If her main pic happens to be a sultry, look-at-me selfie, Spira suggests flipping through her other pictures to make sure they're not all the same. One selfie is fine, but a parade of them is a red flag for a high-maintenance narcissist.

Interestingly enough, while women probably take more selfies on average, men are more likely to use a selfie as their main profile picture than women, Spira says. That's not always a good idea: "Selfies aren't that flattering—they're usually not your best photo," Spira adds.

In fact, on some apps, a selfie can deter people from swiping or "liking." Instead, choose these types of photos to get the most interaction. (Hint: Half-naked beach photos are out, and black-and-white pics are in.)

What it means if: She's showing it all off

"When most guys see a girl in a bikini on a dating profile, they think lingerie," Spira says. Another way of putting this: You know she'll look good naked because she's sporting a barely-there bikini in her profile pic.

But just because she's basically wearing water-ready lingerie doesn't mean she's necessarily looking for that kind of attention. Force your eyes away from her bikini-clad body for a second and look at the context—if there's more landscape than lady, she's probably just trying to show off her adventurous, beach-loving spirit, Spira explains. If she's just rolling around in the sand like a mock Sports Illustrated model, her intentions might be a little more physical. Ultimately, it could just be that she's confident in her body—and we respect the hell out of that.

What it means if: There are multiple women in the photo

Group photos are tricky to decipher. You're stuck playing Guess Who?, flipping through the photos in a process of elimination to figure out which of the women she is.

But a fun group photo isn't necessarily a bad thing, provided she's got some solo pics on her profile. In fact, people who post group photos on social media are more likely to be agreeable and extraverted, a recent study from the University of Pennsylvania suggests.

If she happens to be sharing her profile pic with just one other person and that person is a guy, however, you'll definitely want to flip through her other photos before swiping right. "One picture of her with another guy isn't necessarily a red flag," Spira says. "But if she has multiple pictures with other men—especially on a dating app, where it's pretty obvious this would be a turn-off—you have to wonder what might be going on." Is it a sibling or a boyfriend? You don't know—so unless you're ready to tangle with her past, think twice about letting her into your future.

What it means if: She's got a pet in the pic

If you're browsing Tinder, approximately 10% of the photos you swipe through will feature pups. According to the dating app's internal data, women are as likely as men to pose with their dog. But what does this tell you (aside from the fact she's not heavily allergic to canines and probably doesn't live with a horde of cats)?

"For some, photographs with dogs may signal she's kind, compassionate, or capable of potentially caring for children in the future," says Tinder's resident sociologist, Jess Carbino, Ph.D.

That, or it's someone else's dog. Either way, you have an instant conversation starter.

What it means if: She's wearing sunglasses

OK, yes: Sometimes it just makes sense to wear sunglasses.

Take note, though, if she's concealing her eyes, hair, or half her face with accessories in multiple photos. "If she's covering them up, it might mean she's hiding something," Spira says. 

The same goes for other "bad" photos, Spira says. Here's why: "These days you have so many opportunities to get photos of yourself," she explains. "There's just no good excuse for a main photo to be blurry or cutting off parts of your face." The whole point of dating apps is to get yourself out there and meet new people. If she's luring people in based on misleading photos, it's not a great sign.

The bottom line

Always check her other photos, read her profile, and give her the benefit of the doubt.

Her profile picture is the first attention-grabber, but it's not the only thing you should be looking at. Always take a trip through her other photos. "If she's not using all six photos on Tinder or the maximum number of photos on any other dating app, that signals she's not really serious about meeting someone," Spira says. "Nobody just puts up one or two photos and expects to get matches."

People who want to find a potential partner are going to make the effort to fill out their bio, select a range of photos that represent who they are as best as possible, and be genuine overall. Anything less, and you might be better off looking elsewhere.