Most services also encourage members to add photos or videos to their profile.
Looking beyond the never-married population, 19% of those who are currently divorced, separated or widowed report ever using online dating.
This is up from 11 percent of adults who said the same in 2013.
The increase was most evident in the 18-24 age group, which saw its adoption of online dating sites or mobile dating apps nearly triple from 10 percent in 2013 to 27 percent in 2015.
They'd graduated from the same college, had nearly 20 friends in common on Facebook and still might never have met had it not been for a popular mobile dating app.
Megan, 25, said she is a "big fan" of such dating help. Finding a date hasn't hinged primarily on chance encounters or "setups" by friends since the advent of online dating sites and mobile dating apps.