FORTUNE - Feb 14 - Over the years, eHarmony has added photos and made its clunky interface easier to navigate. That, however, hasn't stopped Tinder and Bumble from stealing users away. "People do end up on those sites looking for relationships, and we see that as our challenge," says eHarmony CEO Grant Langston. Langston says users like the "swipe friendly" dating apps because they are "cheap and easy." But they don't have 16 years worth of rich data. eHarmony collects demographic data, psychographic data (likes, interests and habits), and behavioral data (actions taken on the site). eHarmony's research team also conducts research on couples who met through the site. eHarmony's in-house psychologists and data scientists feed that information into machine learning algorithms that help match compatible users. "That data lets us optimize the site and the process for a number of variables," Langston says.