A phpBB 3.1/3.2/3.3 extension that modifies the attributes of links within posts (and/or private messages) based on whether the links are internal or external. This allows setting different classes so internal and external links look different, setting a target so links open in a new window, setting a nofollow, prefixing URLs such as to add an anonymizer or monetizer, and more.
ext directory of your phpBB board so that you have ext/primehalo/primelinks.Customise -> Manage extensions.Prime Links under the Disabled Extensions list, and click its Enable link.Extensions -> Prime Links.