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Double opt-in means a subscriber confirms their sign-up twice: once on your form, and once by clicking a link in a confirmation email. Only after that click do they join your list. It proves that the address belongs to the person who signed up, and it keeps typos and fake addresses off your list.
Opt-in in general means someone says yes to your emails before you send them. In Belgium, and under the EU ePrivacy rules generally, that is the rule for email advertising: prior, free, specific and informed consent, which you must be able to prove. A pre-ticked box or a line in your terms is not enough. The opposite is opt-out: you email everyone until they unsubscribe, which is only allowed within the exceptions, such as for existing customers.
Three kinds of opt-in
| Kind | What the reader does | Proof | When |
|---|---|---|---|
| Single opt-in | Enters an address and ticks a box | Date, source, form text | Most forms |
| Double opt-in | Then confirms through a link in an email | Date of sign-up and of confirmation | When you want certainty the address is theirs |
| Soft opt-in | Bought from you and could refuse at collection | The purchase and the chance to refuse | Existing customers, similar products |
Soft opt-in is the name for the existing-customer exception. In Belgium it sits in the Royal Decree of 4 April 2003: you may email customers about similar products of your own, if you got their address in a sale and they could refuse free of charge at that moment. The UK has a similar rule under PECR.
A double opt-in email example
The confirmation email is short. A subject such as "Confirm your sign-up", one line on what the reader will get and how often, one button to confirm, and a line saying that nothing happens if they ignore it. No offer, no newsletter content: this email has one job. Most tools let you switch double opt-in on per list, and send the confirmation email for you.
Single or double opt-in
- Steps
- Single opt-inOne: sign up
- Double opt-inTwo: sign up and confirm
- List
- Single opt-inGrows faster
- Double opt-inGrows slower, with fewer wrong addresses
- Proof
- Single opt-inForm and date
- Double opt-inForm, date and a click from the inbox
- Legally required
- Single opt-inEnough in Belgium if you keep the proof
- Double opt-inNot required there, but stronger proof
What each country asks
Most EU countries do not require double opt-in by law, but it is the safest way to prove consent. In Germany it is the common practice for email marketing, because courts there ask for strong proof of consent. In Belgium, single opt-in is enough if you keep the proof. If you sell across borders, double opt-in saves you from checking each country.
Proving consent
Keep the date, the source and the text next to the box for each contact. A newsletter tool does that by itself for sign-ups through its form. For an import from your till or CRM, you track it yourself. When you move to another tool, take those fields with you, or you lose your proof. How to handle that is in Mailchimp alternatives.
Opt-in and delivery
A list of people who said yes arrives better. Since 2024 Gmail and Yahoo ask bulk senders to keep spam complaints under 0.3 percent and to allow one-click unsubscribe. Emailing addresses without consent brings more complaints and lands you in spam sooner. Read why emails go to spam and set up your domain with SPF, DKIM and DMARC.
Opt-in on your landing page
A sign-up often comes through a landing page with a guide, a checklist or a webinar. That is lead generation, and it is allowed, as long as the reader knows they also sign up for your emails and chooses that separately. Making a download depend on a box for advertising is not free consent. Keep the newsletter box apart from the download, and record which page brought the address. That way you also learn which content marketing brings subscribers.
A good sign-up form
A field for the address, a box that is not pre-ticked, a line on what the reader gets and how often, and a link to your privacy policy. That is all. What else belongs on your site is in the GDPR website checklist. To start with a free tool, read create a newsletter for free, and to see how opt-in fits a bigger plan, email marketing strategy. Want the form, confirmation email and list set up for you? See our email marketing services or ask us.
The questions that come back
What is the difference between single and double opt-in?
With single opt-in, the sign-up on your form is enough. With double opt-in, the subscriber also confirms through a link in an email.
Is double opt-in required under the GDPR?
The GDPR does not name it. It asks that you can prove consent, and double opt-in is the strongest proof.
May I email my customers without opt-in?
About similar products of your own, if you got their address in a sale and they could refuse then. Every email needs an unsubscribe link.