Glossary
Confirmed opt-in
Also called double opt-in, DOI.
Last reviewed 18 September 2026
What is confirmed opt-in?
Confirmed opt-in, usually called double opt-in, is the practice of sending one message to a newly submitted address and adding it to a list only after somebody clicks the link in that message.
The word “double” is a misnomer and it has caused real confusion, because it sounds like a second form or a second act of typing. It is one extra click, in a message the reader was expecting, within seconds of asking for it.
It costs a share of sign-ups, typically a fifth to a third, and the loss is concentrated in the addresses you would not have wanted: the mistyped, the borrowed, the reluctant and the automated. What it buys is a list on which every address was reachable and somebody at it asked for the mail, which is what holds a complaint rate below the level the providers enforce.
A confirmation click is also the most durable consent record available. A form submission proves that a browser sent you a string; a click in a message delivered to the address proves that whoever reads that mailbox wanted this.
See also
- Single opt-in
Single opt-in means an address starts receiving mail as soon as it is typed into a form, with nothing in between to establish that the person who typed it owns the mailbox it points at.
- Consent record
A consent record is the evidence that a particular person agreed to receive a particular kind of mail, kept because Article 7(1) of the GDPR puts the burden of demonstrating consent on whoever relies on it.
- Spam complaint rate
A spam complaint rate is the count of people who pressed the spam or junk button divided by the mail delivered to that provider over a window it chooses, and Google and Yahoo both name 0.3 per cent as the level to stay under and 0.1 per cent as the level to aim at.
- Opt-in page
An opt-in page is a page whose only job is to describe one thing and collect an email address for it, and a dedicated one commonly converts 15 to 30 per cent of its visitors where an inline form in a sidebar converts 1 to 3 per cent.
Read next
This term is covered properly in Confirmed opt-in (double opt-in): what it costs, and what it buys, which is a longer piece on the subject.
Every other term is on the glossary index , the longer writing is in the guides, and what this site itself does is on the home page.
Thinking of writing one of these?
5dayemail hosts a five-to-ten day email course: you write it once, and everyone who joins your list gets one email a day, in order, starting from the day they confirm.
Accounts are opened a few at a time rather than by signing up. Leave your address and you will be written to when the next ones open.
One message, when there is room. No course emails, no newsletter, and the address is not passed on. Ask and it is deleted; what is kept, and for how long, is in the privacy policy.