What is double opt-in (DOI)?

Double opt-in (DOI), also called confirmed opt-in, is a subscription method that adds a verification step after the initial signup. When a user submits their email address through a signup form, they receive a confirmation email containing a unique link. Only when the subscriber clicks that link is their subscription finalized and their address added to the active mailing list. This two-step process ensures that the person who submitted the form actually controls the email address and genuinely wants to receive your communications.

The DOI workflow typically includes three stages: form submission, confirmation email delivery, and verification click. The confirmation email should clearly explain what the subscriber is confirming, include a prominent call-to-action button or link, and often restates what types of emails they'll receive. Best practices include setting an expiration period for the confirmation link (commonly 24-72 hours) and sending a reminder if the link hasn't been clicked within a reasonable timeframe. Subscribers who never confirm are either not added to the list or kept in a pending state and eventually purged.

DOI is considered the gold standard for list hygiene because it validates both email address accuracy and subscriber intent. Every confirmed address represents a real person who deliberately chose to join your list, which typically results in higher engagement rates, fewer spam complaints, and better deliverability. Some jurisdictions and industries effectively require DOI-Germany, for instance, has strong legal precedents favoring confirmed opt-in as proof of consent. Double opt-in may cost you some signups upfront, but it builds a foundation of verified, engaged subscribers who actually want to hear from you.