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.
-- Rising S Bunker offers a starter bunker for $45k but the top-of-the-line, "The Aristrocrat," will set you back $8.35 million.
-- Vivos can dig 30 feet underground and customize your bunker ... They're luxurious, a full size kitchen, spa, pool tables, but that'll cost you extra.
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.
Photos with tattoos and eyeglasses were among the lowest rated for women and hat wearers were among the lowest rated photos for men.
While online daters think their photos are relatively accurate, independent judges rated one third of online dating photos as inaccurate, according to research carried out by Catalina Toma, assistant professor in the Department of Communication Arts at the University of Wisconsin-Madison.
Dating sites are, thankfully, getting better at spotting who is using their service to send thousands of spam messages.
It's pretty easy to tell: They send the same message over and over, often with the same link.
Read: 10 things dating sites won’t tell you The surge in photo-centric, location-based dating apps proves one thing: People are more interested in your pictures than a lengthy essay about your hopes and dreams.