Some sites such as Ok Cupid.com, and are free and offer additional paid services in a freemium revenue model.
Some sites are broad-based, with members coming from a variety of backgrounds looking for different types of relationships.
Some sites provide free registration, but may offer services which require a monthly fee.
Other sites depend on advertising for their revenue.
As online dating's population becomes larger, sites with specific demographics are becoming more popular as a way to narrow the pool of potential matches.
The 20 most popular dating sites in 2006 as ranked by Hitwise include j (for Jewish singles), Christian Mingle.com, Christian Cafe.com, Man (same sex introductions), Love From India.ini, Black Christian People Meet.com, (for Latino singles), Asian People Meet.com, and (for Indian singles).
Online dating sites use market metaphors to match people.
Match metaphors are conceptual frameworks that allow individuals to make sense of new concepts by drawing upon familiar experiences and frame-works.
Most sites allow members to upload photos or videos of themselves and browse the photos and videos of others.
Sites may offer additional services, such as webcasts, online chat, telephone chat (VOIP), and message boards.
This metaphor of the marketplace – a place where people go to "shop" for potential romantic partners and to "sell" themselves in hopes of creating a successful romantic relationship – is highlighted by the layout and functionality of online dating websites.
The marketplace metaphor may also resonate with participants' conceptual orientation towards the process of ﬁnding a romantic partner.
Since 2003, several free dating sites, operating on ad based-revenue rather than monthly subscriptions, have appeared and become increasingly popular.