Yes/No; While it is free to use, POF offers premium services as part of their upgraded membership, such as seeing the date and time a user viewed your profile and allowing you to see whether a user read and/or deleted your message.
, meaning more people visit these online dating sites on a monthly basis.
With an (estimated) 35 million unique monthly users, has the largest active membership of all the dating sites out there - and for good reason, however with some caveats: it's geared more towards folks looking for long term relationships, you'll want to carefully craft your profile to focus on such, and make sure you carefully review all emails for potential romance scams, as Match seems to attract more than their fair share of mysterious strangers trapped in Nigeria.
More » The largest of the free dating sites, POF boasts an (estimated) 23 million unique members using the site every month.
With 1.7 million unique monthly members and the support of People Media (one of the largest online dating website conglomerates), and (also its parent company) Our Time a definite must-see if you're wanting to date or remarry in your 50s and beyond.