PlentyofFish.com

Price: Free.
 Users per month*: 2.75 million.
 Registration time: 12.5 minutes.
 Pros: Costs nothing; easy to use; has a huge pool of people to flirt and connect with; boasts 120,000 marriages a year.
 Cons: Distorted or fuzzy images; unattractive website.
 
 

Match.com

Price: $30 per month.
 Users per month*: 2.75 million.
 Registration time: 15 minutes.
 Pros: Simple to navigate; finds matches based on keyword descriptions; provides apps for smartphones.
 Cons: Poor screening techniques.
 
 

True.com

Price: $50 a month.
 Users per month*: 2.5 million people.
 Registration time: 10 minutes.
 Pros: Safer than some sites, since members must submit to a background check; has a fun, flirty environment.
 Cons: Tacky advertisements.
 
 

EHarmony.com

Price: $60 a month.
 Users per month*: 1.75 million.
 Registration time: 25 minutes.
 Pros: They do the matching for you, based on a detailed questionnaire; an advice section with expert and member tips.
 Cons: Generic profiles; more expensive than other sites.
 
 *The numbers for users per month are based on research by ComScore.