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Email Marketing Glossary.

Clear, no-fluff definitions of every email marketing term that matters—from open rates to double opt-in. 

 

Single Opt-In

Single opt-in is a signup method where a subscriber is added to your list immediately after submitting a form, without a confirmation step. It maximizes signups but can let in invalid addresses.

Also known as: single opt-in, SOI

Single opt-in favors growth and simplicity: submit the form, you're subscribed. It captures the most signups, but without a confirmation step, it also lets through typos, fake addresses, and the occasional spam trap.

How does single opt-in work?

A visitor enters their email in a form and is added to your list right away — no confirmation email required before they start receiving your mail.

Single opt-in vs. double opt-in

Single opt-in captures more subscribers instantly but with lower list quality. Double opt-in requires a confirmation click, producing a cleaner, more engaged list at the cost of some volume.

When is single opt-in a good fit?

When maximizing list size matters and you have other safeguards (validation, engagement monitoring). In stricter-consent regions, double opt-in may be the safer choice.

Related terms

Email List Lead Magnet List Segmentation Subscriber Opt-In Form Double Opt-In

Related reading from Drip

Single Opt-In vs. Double Opt-In: Which is Best for Your Email List?

Frequently asked questions

What is single opt-in?
Single opt-in is a signup method where a subscriber is added to your list immediately after submitting a form, with no confirmation step. It maximizes signups but can allow invalid or mistyped addresses through.
What's the difference between single and double opt-in?
Single opt-in adds subscribers instantly without confirmation, capturing more signups but lower quality. Double opt-in requires clicking a confirmation link, producing a cleaner, more engaged list with slightly fewer subscribers.
Is single opt-in bad for deliverability?
It carries more risk than double opt-in because it can admit typos, fake addresses, and spam traps. You can mitigate this with address validation and active engagement monitoring, but list quality tends to be lower.
When should I use single opt-in?
Single opt-in suits situations where maximizing list size is the priority and you have safeguards like validation in place. In regions with strict consent requirements, double opt-in is often the safer choice.
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