Double opt-in
Synonym for confirmed opt-in — user must click a verification link before being added to the list.
Double opt-in is the same as confirmed opt-in: a subscription flow where the user submits their email, then must click a verification link in a confirmation email before being added to the marketing list. The "double" refers to the two affirmative actions (submit, then confirm).
Double opt-in is the gold standard for list hygiene and consent. It eliminates typos, blocks form-spam, and creates auditable proof of opt-in for regulatory compliance. The cost is a ~10–25% drop in completed signups versus single opt-in, since some users never click the confirmation link.
For most marketing lists, double opt-in is worth the conversion hit. For very high-intent flows (paid trials, gated downloads), single opt-in with strong list hygiene is sometimes defensible. The decision depends on regulatory exposure, list value per subscriber, and tolerance for stale-list problems down the line.