When someone fills in your signup form, you have two choices. You can add them to your list straight away (single opt-in), or you can send a confirmation email first and only add them once they click the link inside (double opt-in).
It sounds like a small setting. In practice it shapes how clean your list stays, how your emails land and how much proof you have that people actually asked to hear from you. Here’s how to decide for a small list.
What Double Opt-In Actually Does
Mailchimp describes double opt-in as an extra confirmation step: after someone submits your form, they get an email with a link, and they’re only added as a subscribed contact after they click it. Single opt-in skips that step, so the address goes on your list the moment the form is submitted.
Most email services offer both. Defaults differ: Kit’s help center says double opt-in is its default setting and recommends using it on all forms and landing pages, while other services leave the choice to you or set it based on your account details. Check the form settings in whatever tool you use rather than assuming.
The Case for Double Opt-In
Fewer Typos and Fake Addresses
If someone mistypes their address, the confirmation email never reaches them, so the bad address never joins your list. Kit’s documentation makes this point directly: confirming each subscriber keeps a list more accurate, so mistyped addresses don’t pile up and bounce.
It also helps against bots. Mailchimp explains that spambots scan the web for signup forms and submit made-up information, which distorts your statistics and can hurt your sending reputation. A bot that submits a random address can’t click a confirmation link in an inbox it doesn’t control. (Mailchimp also uses other protections, such as reCAPTCHA and hidden “honeypot” fields, on its forms.)
Subscribers Who Clearly Want Your Emails
Someone who takes the extra step to confirm has shown real interest. Both Kit and Mailchimp say this tends to help engagement, and Kit links it to better deliverability, because mailbox providers pay attention to how people interact with your emails. Engagement is only part of the picture; our plain-words guide to SPF, DKIM and DMARC covers the technical side of reaching the inbox.
A Clear Record of Consent
If you have subscribers in the European Union, the GDPR applies to how you handle their data. Article 7(1) says that where processing is based on consent, the business must be able to demonstrate that the person consented. The regulation doesn’t name double opt-in specifically, but a confirmed click, with a time stamp kept by your email service, is a straightforward record to point to. This is general information, not legal advice; rules vary by country, so check official guidance if you have international subscribers.
The Case for Single Opt-In
The main argument for single opt-in is simple: some people never confirm. The confirmation email can land in a spam or promotions folder, arrive late or simply be ignored. Mailchimp notes that some webmail programs can delay bulk mail by up to 24 hours. Every unconfirmed signup is someone who wanted your lead magnet and didn’t get on your list.
Kit, which strongly favors double opt-in, still names a few cases where single opt-in can make sense: live events, a small hand-picked group, or internal forms that aren’t shared publicly. In other words, situations where you already know the people and their addresses are almost certainly correct.
How to Choose for a Small List
For most people building a list on the side, double opt-in is the safer default. A small list with real, engaged readers is worth more than a bigger list padded with typos and bots, and you’ll spend less time cleaning it later.
Consider single opt-in only if:
- You collect addresses in person or from people you already know.
- Your form is protected against bots in other ways and you check new signups for junk regularly.
- You’ve measured a confirmation rate so low that it’s clearly costing you real subscribers, and you’ve already tried improving the confirmation email.
Make the Confirmation Step Easy to Finish
If you use double opt-in, the confirmation email becomes one of the most important emails you send. A few practical improvements:
- Tell people what happens next on the thank-you page. Something like: “Almost done. Check your inbox for an email from [your name] and click the button to confirm. If you don’t see it in a few minutes, check your spam or promotions folder.”
- Use a recognizable sender name. Use your own name or your business name, whichever people saw on the signup form.
- Write a plain, specific subject line. “Confirm your email to get the [freebie name]” beats something clever.
- Keep the email short with one obvious button. The only job of this email is the click.
- Deliver the freebie after confirmation. Kit’s confirmation email (also called the incentive email) can hand over a download or send people to a thank-you page once they click, which gives them a clear reason to confirm. Other services offer similar options.
- Test the whole flow yourself. Sign up with a personal address on your phone and see how long the email takes, where it lands and how it looks.
Check Your Numbers Once a Month
Your email service should show how many people signed up and how many confirmed. If a large share of signups never confirm, look at the thank-you page and confirmation email first before switching off double opt-in. Small wording changes often matter more than the setting itself. Mailchimp, for example, only adds someone as a subscribed contact after they click the confirmation link, so judge your growth by confirmed subscribers, not form submissions.
Finally, remember that consent at signup is only the start. Our guide to list hygiene covers keeping a list healthy after people join.
Do This Today
Sign up for your own list using a personal email address on your phone. Time how long the confirmation (or welcome) email takes to arrive, note which folder it lands in, and rewrite your thank-you page so it tells new subscribers exactly what to look for.
More on Totally Relentless
- SPF, DKIM and DMARC in Plain Words: Keep Your Emails Out of Spam
- List Hygiene for a Small Email List: When and How to Clean It
- How to Write a Welcome Email That Sets the Right Expectations
