Double opt-in vs single opt-in: which should you use?

What single opt-in does

With single opt-in, the address joins your list the moment the form is sent. There are no extra steps, so your list grows faster, but it also collects typos, fake addresses and people who never meant to sign up.

What double opt-in does

With double opt-in, the person gets an email with a confirmation link and joins your list only after clicking it. Some people will never confirm, so you get fewer contacts, but the ones you get have proved the address is theirs.

What each one costs

The main cost of single opt-in comes later. Bad addresses raise your bounce rate, and people who forgot signing up mark you as spam, and both hurt your sending reputation. It also leaves your form open to abuse by bots.

The cost of double opt-in is at the start: every confirmation that goes unclicked is a contact you do not get.

What the law says

Neither GDPR nor CAN-SPAM names double opt-in as a requirement, but under GDPR you must be able to prove consent, and a confirmation click is strong proof. Rules differ by country, and in Germany double opt-in is the accepted standard, so check what applies to your audience.

How the confirmation flow works

A double opt-in flow has three steps. The person submits your form and sees a page telling them to check their inbox. They receive a confirmation email with one link. When they click it, you mark the contact as confirmed and they start receiving your emails.

Until that click happens, the address should stay unconfirmed and out of your campaigns. Sending to it anyway removes the whole benefit.

How to write a confirmation email that gets clicked

The confirmation email is short, and its only job is to get one click. The reader just left your site, so it should arrive within seconds and be obvious.

• Subject: say what to do, such as Please confirm your email address
• Sender: use the same brand name the person saw on the form
• Body: one or two lines explaining why they got the email
• Link: one clear button or link, and nothing competing with it
• Footer: say that they can ignore the email if they did not sign up

How to lose fewer confirmations

Some people will not confirm no matter what, but most losses have simple causes. After the form, tell the person exactly what happens next and mention the spam folder. Make sure your domain is authenticated with SPF and DKIM so that the email reaches the inbox.

Check the confirmation rate from time to time. A sudden drop usually means the email is landing in spam or a link broke, and without looking you may not notice for weeks.

What to do with an existing single opt-in list

You do not need to reconfirm everyone at once. Start by sending to the people who opened or clicked recently, and remove addresses that bounce. For people who have not engaged in a long time, send one email asking if they still want to hear from you, then remove anyone who does not respond.

A smaller list that reads your email is worth more than a large one that ignores it, because mailbox providers watch how people react to your messages.

How to choose

Use double opt-in for public forms, for audiences in the EU and whenever list quality matters more than volume. Single opt-in can make sense when the address has already been verified, such as a signup inside your own product.

Using it in Reloops

Reloops can send a confirmation email to new contacts from your signup forms, and you can edit that email in Settings.