Read Time: 7 min

Single Opt-In vs. Double Opt-In: The Case for SOI


We gather here to settle once and for all the debate as to whether single opt-in or double opt-in is the better signup process. Before we begin, let’s be clear on what these two terms mean:

  • Single opt-in (SOI) is a subscription process where a new email address is added to your mailing list without requiring the owner of that email address to confirm definitively that they knowingly and willingly opted in
  • Double opt-in (DOI), also known as confirmed opt-in (COI), is a subscription process where a new email address is only added to your mailing address after the email address owner clicks a confirmation link in a subscription activation or opt-in confirmation request email that’s sent to them after they opt in via a form or checkbox

With that out of the way, let’s now hear the case for single opt-in…

Opening Statement

Some will argue that SOI vs. DOI is a case of quantity vs. quality, but it’s really a case of list productivity. Single opt-in is the superior subscription process because it maximizes list growth and overall performance by minimizing signup barriers and opportunities for errors.

(I have kept my opening statement short and simple, just like a good single opt-in process.)

Presentation of Evidence and Testimony of Witnesses

Exhibit A: Single opt-in minimizes barriers to subscribing.

The more friction in a process, the fewer people that will complete it. Nothing kills a completion rate like lots of form fields, long answers, and too many steps.

Double opt-in is simply one step too many. We see that in the confirmation failure rates, which are generally in the 20% to 40% range. Those aren’t just numbers. Those are lots of genuinely interested people who will be disappointed when they don’t receive your emails because they didn’t see your subscription confirmation request email, or saw it but didn’t understand what they had to do to confirm.

Let’s be generous and assume only 20% of would-be subscribers don’t confirm their subscription. In that case, your list would grow 25% faster using single opt-in rather than double opt-in. That’s a lot of growth to leave on the table.

Exhibit B: Single opt-in has lower failure rates.

More complex processes have more points of failure. That’s the case with double opt-in as well.

The failure rate of homepage email signup forms that used double opt-in is around 27%, according to research I did involving 160 B2C brands. That’s nearly twice the overall opt-in process failure rate of 15%.

Keep in mind that study only looked at homepage email signup forms, which you’d hope would be one of the email address acquisition sources that marketers are doing consistent upkeep on. Given that, it seems likely that failure rates might be even higher on other, more far-flung email address acquisition sources.

Add the potential for opt-in failures on top of the process incompletion rate and double opt-in is a very leaky system.

Exhibit C: Single opt-in produces more engagement.

Here’s where the argument of list quality comes into play. Double opt-in lists will always have higher open rates, click rates, and conversion rates than single opt-in lists. That makes sense because these subscribers have demonstrated they’re both willing and able to jump through additional hoops in order to receive your emails.

However, what’s also true is that single opt-in lists will always generate more opens, clicks, and conversions than double opt-in lists. That’s because a single opt-in list includes everyone who would have completed a double opt-in process and then some.

So ask yourself: Would you like higher performance rates or higher total performance? Better yet, ask your CEO or CMO which they would prefer.

Exhibit D: There are other, less burdensome ways to protect the quality of your list.

In addition to generating more committed subscribers, double opt-in is also praised for protecting email lists from typos, bots, malicious signups, and people with subscriber’s remorse. While it’s true that double opt-in does that, there are other methods that achieve similar results while adding much less friction to the process or none at all. For example…

  • Double entry confirmation requires would-be subscribers to enter their email address twice in two different fields. This method requires a little bit more effort to subscribe, but that extra effort takes place on the signup form rather than in the inbox as with double opt-in. Double entry confirmation helps reduce the number of typos in email addresses, and may also thwart some bot activity.
    Kohl's uses double entry confirmation
  • Email verification tools from BriteVerify, Fresh Address, and others check the email addresses submitted to ensure they don’t contain a bad format, bad domain, or bad account. These tools will reduce your hard bounce rate.
  • Removing subscribers that fail to engage is another way to improve your list hygiene. We call new subscribers that never engage with your emails Never-Actives and recommend sending them a re-permission email if they haven’t opened or clicked any of your emails during their first 4 months on your list or any of the first 10 emails they receive, whichever comes first. Like a subscription confirmation request email, a re-permission email asks the subscriber to confirm their opt-in by clicking a link in the email or else you stop emailing them.

In addition to considering those methods, marketers should examine their permission practices for each of their email address acquisition sources, plus the language they use and the expectations they set on their signup forms, signup confirmation pages, and their welcome emails. Chances are that most of your problematic signups get onto your list through one or two acquisition sources. Determine if those sources are worth the risk they pose.

Witness No. 1: Litmus

We use single opt-in here at Litmus for all of our newsletter signups. Feel free to try it for yourself and experience the simplicity of single opt-in:

Subscribe to our newsletter and get the latest content for email marketing pros delivered straight to your inbox.

For the signup forms that are hosted by our ESP, Pardot, they provide some email verification. And for subscription forms that are hosted elsewhere, we use BriteVerify to catch typos and defend against bot activity. Those tools help us minimize the risks. Currently, our deliverability is consistently above 99% and we’re working toward getting it consistently above 99.5%.

Additional Witnesses?

If you would like to testify on behalf of single opt-in, please submit your comments below.

Closing Arguments

Email address typos, malicious signups, and bots all pose very real threats. But double opt-in is a hatchet when what you really need is a nice set of scalpels to address the risks around single opt-in.

The bottom line:

  1. Single opt-in provides a much simpler and cleaner subscription process for both the subscriber and the marketer.
  2. A single opt-in list beats a double opt-in list every time on total engagement, so long as you wisely mitigate the risks with clear permission language, good list hygiene, and sensible management of inactive subscribers.

I rest my case.

Before You Make Your Decision…

Hear both sides of this debate, what your marketing peers think, and the final verdict:

Make it to the inbox, not the spam folder

Identify issues that might keep you from the inbox and get actionable help for how to fix them with Litmus Spam Testing.

Try Litmus free →