Opt-in
Opt-in is a consent model in which nothing happens until the person actively agrees, so a tracker, a marketing email or a data use stays off by default and is switched on only by the person's choice.Opt-in is the European default for cookies and electronic marketing. Article 5(3) of the ePrivacy Directive makes storing or reading non-essential information on a device conditional on consent, and Article 13 does the same for most marketing emails and text messages to individuals. Because consent under the GDPR must be an unambiguous, affirmative act, an opt-in cannot be built from a pre-ticked box, from silence or from continued browsing.
On a website, opt-in means three things in practice. Optional categories start switched off. Scripts and embeds for those categories wait until the visitor accepts, which is the prior consent requirement. And the visitor can later reverse the choice as easily as they made it.
Opt-in is not limited to the EU. The UK, Brazil and Türkiye apply it to non-essential cookies, and several US state laws use it for narrow cases even though their general model is opt-out: Virginia, Colorado and Connecticut, for example, require consent before processing sensitive data. The two models can coexist on one site through geo-targeting, with an opt-in banner for visitors from Europe and an opt-out notice for visitors from US states.