The term “opt-in” comes up a lot in online marketing. Single opt-in and double opt-in are two different methods of consent, most often used in relation to email. And in a way, people “opt-in” to your marketing in a variety of ways, including following you on social media. But when we talk about opt-in advertising, we’re talking about users who are opting in to your email list through an ad shown on a third-party site, typically through a co-registration form where their information has already been pre-populated for an easy opt-in. So while there are many ways to opt-in to marketing messaging, here are three reasons to specifically choose opt-in advertising for your next lead generation campaign.