Ms. Mahdara envisioned a new experiential retail model. “There’s a lot of stuff for music and a lot of stuff for gaming and a lot of stuff for sports,” Ms. Mahdara said. “What became abundantly clear to me is that there was nothing for young women and people in general who were interested in beauty but not sure how they fit into that world.” Her goal was not just an offline experience but a marketplace, one that would translate into sales for participating beauty companies.

In 2014, Beautycon added New York to its lineup; by 2015, Dallas and London joined the list. (London is still in the mix; Dallas is not.) In 2016, the Los Angeles event was big enough to move into the convention center and last year it expanded from one day to two. This year has been a tipping point of sorts, starting with the two-day New York show warranting space in the sprawling Javits Center, and big brands like MAC and Target coming on board.

Traditional celebrities signed on, too, and their appearances on the main stage have drawn headlines and more publicity for Beautycon. The keynote by “Black-ish” actress Tracee Ellis Ross in Los Angeles last year about expanding the definition of beauty — “I’m inviting you to let your ‘you’ flag fly,” she said — became fodder for a later appearance on Conan O’Brien.

“Moj and her team recognize that beauty is about more than just slick advertising,” Debra Perelman, the chief executive officer of Revlon, said in an email. They “realized early that in the digital age you can’t just talk to women, but instead need to build a deep, personal relationship with them.”

‘This is the Future of Beauty’

Beautycon is a festival, yes, but it’s also a data-gathering machine. Two hundred beacons sprinkled throughout the floor in Los Angeles allowed organizers to heat-map the crowds, showing where the largest groups of attendees were congregating. Beautycon held eight focus groups each day that weekend, talking to 320 consumers about their shopping habits and attitudes on health and wellness. Each wristband was equipped with radio-frequency identification (R.F.I.D.) technology, allowing the organizers to monitor the path people took, how long they lingered, and if they visited a booth multiple times.

Coupled with registration information, Beautycon can paint a detailed picture of these shoppers. “We know what she wants, we know what she’s missing, we know what she needs,” said Richelieu Dennis, the chief executive of Sundial Brands, owner of Essence magazine and a Beautycon investor.

Beautycon’s connection to customers, paired with the combination of content and commerce, has helped Ms. Mahdara raise $20 million from investors. The most recent round of financing raised $6 million, led by the New Voices Fund, a $100 million fund that invests in businesses owned or managed by women of color and run by Mr. Dennis. “This is the future of beauty — this is the future of business,” he said of Beautycon.