Double opt-in asks new subscribers to confirm by clicking a link in an email before they join your list. It sounds like friction. In practice it is one of the cheapest ways to protect your deliverability.
What you lose
Some people never click the confirmation link: they mistyped their address, signed up on a whim, or the email landed in a tab they never open. Expect a share of signups to stay pending.
What you gain
- No typos or fake addresses. Mistyped domains bounce, and bounces hurt your reputation with mailbox providers.
- No spam traps. Pristine traps are addresses that never signed up for anything. They cannot confirm, so they never reach your list.
- Proof of consent. You know when and how each person agreed, which matters under GDPR and similar laws.
- Better engagement. People who confirm actually want your emails, so open and click rates start higher.
Make the confirmation email count
Keep it short, say what they signed up for, and make the button obvious. Send it immediately; the longer people wait, the fewer confirm. Then follow up with a welcome email that delivers what you promised.
When single opt-in is fine
If people sign up while logged in to your product, you already know the address works. For everything else, turn on double opt-in in your signup form settings.