Most services offer digital messaging, while others provide additional services such as webcasts, online chat, telephone chat (VOIP), and message boards.

Members can constrain their interactions to the online space, or they can arrange a date to meet in person.

Just two years ago, American adults ages 18 to 24 used online-dating sites and apps at an average rate for all American adults—about 10 percent. College-aged and post-college-aged Americans are now the most likely demographic to turn to the technology.

That’s the most interesting result from a Pew Research Center survey released Thursday on Americans’ online-dating habits.

About 45% of couples met on dating sites; the rest met on online social networks, chat rooms, instant messaging or other online forums.

Lead author John Cacioppo, a psychologist and director of the Center for Cognitive and Social Neuroscience at the University of Chicago, says dating sites may "attract people who are serious about getting married."While Cacioppo is a noted researcher and the study is in a prestigious scientific journal, it is not without controversy.

Online dating (or Internet dating) is a system that enables strangers to find and introduce themselves to new personal connections over the Internet, usually with the goal of developing personal, romantic, or sexual relationships.

An online dating service is a company that provides specific mechanisms (generally websites or applications) for online dating through the use of Internet-connected personal computers or mobile devices.

But a new poll finds that an extraordinary technological change has taken place over the past three years.

Most services also encourage members to add photos or videos to their profile.

Once a profile has been created, members can view the profiles of other members of the service, using the visible profile information to decide whether or not to initiate contact.

"I do think mobile dating is going to be the main driver of this growth."The research, based on a survey of more than 19,000 individuals who married between 20, also found relationships that began online are slightly happier and less likely to split than those that started offline.

Findings, published in the journal Proceedings of the National Academy of Sciences, put the percentage of married couples that now meet online at almost 35% -- which gives what may be the first broad look at the overall percentage of new marriages that result from meeting online.