Ten years ago, if you had snapped a photo of yourself in a public restroom and tried to share it with your friends, you could count on a few dubious looks. Now, you get likes — lots of them.

It’s the age of the Instagram bathroom. Publicity-savvy restaurateurs are catering to millennials by pouring money into powder rooms that are so picture-perfect, customers can’t help but snap a selfie and post it on social media. A search of the hashtag #bathroomselfie on Instagram turns up over 1.3 million images.

“The restaurant business today has to be an experience for the younger people that are [living] on the Internet through their phone,” says Willie Degel, a restaurateur and the former host of Food Network’s “Restaurant Steakout.” When he opened Uncle Jack’s Meat House in Astoria in December, making the restaurant Instagrammable was key.

For the bathroom, which is unisex, that meant installing a 55-inch “selfie mirror” in front of the sinks. The mirror also functions as a touchscreen. Tap it and a cartoon animation of owner Degel appears, goading you to pose for a photo. You can choose one to three frames on your photo strip, and the snaps are sent to your e-mail and printed in a slot (for free!) next to the sink.

“Everybody’s wowed, everybody’s copying it, everybody’s blown away,” says Degel. “The restaurant business is show business.”

Hospitality-industry designers say they’re seeing clients put more resources into powder rooms, with an eye toward making customers snap happy.

“Years ago, [the bathroom] just wasn’t where you put your money in a restaurant,” says John Kole, co-founder and principal at Hecho Inc., who has designed interiors for trendy haunts such as Baby’s All Right, Fine & Rare and Cannibal Liquor House. “Now it’s a little more expected that your budget would be appropriate to design heavily in the bathroom, rather that just providing a clean space.”

Samantha Wasser, co-founder and creative director of fast-casual restaurants the Sosta and By Chloe, says good design equals free publicity.

“Social media is a free tool that I try and play to as much as possible,” says Wasser, whose newest venture, Dez, in Nolita, is drawing likes thanks to a vibrant desert mural on its bathroom walls. “When you’re opening a restaurant, you have such a small budget.”

Others says they didn’t set out to design toilets that could go viral, but they’re happy for the attention.

“Bathrooms have always been … the one place where you’re alone and you can take in your surroundings, so it was important to me that the bathroom be interesting,” says Natalka Burian, part owner of Elsa in Cobble Hill, which opened in early 2017. The chic cocktail bar’s two identical restrooms have backlit, slatted mirrors that give a futuristic fun-house effect that Instagrammers love.

“I did not anticipate that at all,” she says, but she takes it as a compliment. “If people feel so comfortable in the bathroom that they’re taking photos in there … that’s a hospitality win.”

For customers, a beautiful bathroom affords them the opportunity to share their restaurant experience without having to worry about being obnoxious.

“I don’t take selfies in public … because I feel like I would judge the person that does that,” says Alleson Lai, a 26-year-old graphic designer. But the Upper East Side resident isn’t above snapping pictures of herself in the restrooms at Dez, Motel Morris or Lalito. Selfies, she says, are OK as long as they’re “strictly within a private setting, a k a the bathroom.”

At Motel Morris, which opened in April 2017, the rosy bathrooms — featuring vintage floral wallpaper, pink lawn chairs and an old rotary phone — spawned its own hashtag: #peeinpink.

Co-owner and creative director Tamara McCarthy says it happened organically, but they ran with it.

“The hashtag was added afterward, when we realized people were taking a long time in the bathroom, taking pictures and all that,” she says.

Bottom line? Having an establishment without a photogenic bathroom is potentially flushing money down the toilet.

Designer Kole believes the once-modest commode can make or break an entire restaurant concept. He says: “They’re either forgettable or extraordinary.”