S, but is growing in the UK and other parts of Europe.
While it is free to use, Plenty Of Fish offers premium services as part of their upgraded membership, such as who has "liked" a member through the service's Tinder-like Meet Me feature, and allowing users to see whether a message has been read and/or deleted.
The site will log you out a lot for inactivity so always save a copy of any long thought out messages before hitting the send button.
If you have a temporary lapse of brain activity there is a convenient list of date ideas (zoo, comedy show, etc) right next to the send button to help you get to that first date.
In addition, the site requires new joiners to upload a face photo or risk being banned.
This might not be the best for those of us that are shy, but they do have an option to make pictures private.