Overview of the Double Opt-In Process


What is Double Opt-in?

Double opt-in is a process through which a new subscriber must confirm their email address before being subscribed to a given list.

When a Klaviyo list has double opt-in enabled, new subscribers will receive a confirmation email immediately after signing up. This email will prompt them to confirm their subscription. Only subscribers that confirm their subscription will be successfully added to the list.

The Double Opt-in Process Visualized



New subscribers will not get queued up for a welcome series until they have confirmed their subscription via the double opt-in process.

Why is Double Opt-In Important?

When you add a sign up form to your site, you are not able to control who decides to take advantage of this form. Even if you add an extra level of email validation, it isn’t always possible to ensure subscribers only submit valid or accurate email addresses. Well-intentioned subscribers could simply type their email incorrectly, but spam-bots could also find your form and flood it with suspect email addresses.

The double opt-in process helps you grow your list while also minimizing abuse and preventing the accumulation of invalid or mistyped emails. This is important because most major email clients (like Google and Yahoo) track how recipients interact with emails from your domain -- how many emails are marked as spam, how many are opened, how many bounce, etc.

They then use this information to determine whether your emails are classified as spam. This means having a lot of uninterested people or a lot of invalid emails on your list will only hurt your efforts to reach those that actually do want to receive your emails.

Single Opt-In

In some specific cases you may want to remove double opt-in and make your list single opt-in.


The ability to make a list single opt-in is disabled by default and not displayed in all Klaviyo accounts. For customers on a paid plan, contact customer success and request to enable the option to make your lists single opt-in. This feature is disabled by default because we strongly caution against using single opt-in on any of your lists unless you have a specific use case that calls for it.

Most often customers choose to implement single opt-in when they are using other third party signup forms or tools and their customers are prompted with a double opt-in confirmation at some other point in the signup workflow. For example, if your third party signup form has a double-opt in feature enabled, you might want to disable double opt-in on your Klaviyo list so customers don't experience multiple opt-in confirmation emails.

Enable single opt-in on a list by clicking into the list and clicking the Settings tab. From the Opt-in & Unsubscribes settings, uncheck the box next to "Require subscribers to confirm their subscription before being added to your list."


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