How do I make drupal check for similar content? Im using drupal 7 and Im looking for a solution or a module that when a user goes to submit a piece of content they are presented with a "similar content already submitted" list after they enter a title or more specifically a link. 
I want to reduce similar or duplicate nodes on my site. I currently use the link module and I allow users to submit links to my site. Occasionally a user will submit a link that has already been submitted by someone else and I want to help alleviate that. Thanks.
Use the Unique Field module and select your link field as the unique field.