
What is double opt-in?
Double Opt-in is a process that requires from subscribers to confirm their subscription via email. If you have double opt-in enabled, after someone subscribes through one of your forms, he will receive an email from which he needs to confirm his subscription, and only after that he will be placed on your list.

In Klaviyo, the double opt-in process needs to be enabled/disabled for each List separately. By default, each list has the double opt-in enabled.
One very important thing to understand is how this process works. This can be a little confusing if you’re not familiar with how Klaviyo’s list management, so we’ll try to explain it in details.
Every email you capture, whether you have marketing consent or not, Klaviyo will store it as a profile in the “Profiles” section.

One email can exist only once in the “Profiles” section, but it can placed in multiple lists.
When someone subscribes to a list for which you have the double opt-in enabled, they will immediately be placed in the “Profiles” section, and a confirmation email will be sent to them. Only after they confirm their subscription, they will be placed on the list.
This is important to understand because in many situations you can use list as a trigger for some Flow. If that list has the double opt-in enabled, only the subscribers who confirm their subscription will enter the list, hence only those subscribers will enter the Flow.
Do you need double opt-in enabled?
That’s entirely up to you. There’s an up and downside of this process. The double opt-in process is created to protect you. After you place a signup form on your website, you have no control over who can opt-in. One upside is that you will be protected from hackers. There are spam bots that can flood your account with fake email addresses and if you start sending campaigns to them, it can harm your deliverability. Although these attacks are usually targeted towards large brands, there’s no guarantee that it can’t happen to smaller brands too. Occasionally, it can also happen for someone to mistype their email address when they’re subscribing. That can lead to sending campaigns to a non-existing email address or to someone who hasn’t subscribed to your emails. By having double opt-in enabled, you’re protected from these situations.
The downside of this process is that you might miss some subscriptions. If a legit person decides to opt-in to your emails, but they don’t take the extra step of confirming their subscription, they won’t be placed on your list. This means that they won’t trigger the Flows you’ve set in place, and if you’re not specifically segmenting these people, they’ll miss your campaigns too.
Ultimately, it’s your decision whether you want to enable the double opt-in and ensure that all emails you have are legit subscriptions with a strong intend of subscribing or disable the double opt-in and make sure that everyone who subscribes will get a chance to see your emails.
How to disable double opt-in in Klaviyo?
Double Opt-in is enabled by default for new accounts in Klaviyo and can’t be disabled if you’re on the Free Plan. Once you switch to a paid plan in Klaviyo, you can request from Klaviyo’s support team using this contact form to reveal the double opt-in feature for your account, and only then you can toggle it ON and OFF for each different list.
After you get a confirmation that the option is enabled for your account, navigate to the List for which you want to turn off the double opt-in. Open the list and click on “Settings”. From here, in the “Opt-in Process” section, select the “Single Opt-in” option.

Click on the “Update List Settings” button and the double opt-in is disabled for that list.
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