Glossary
Confirmed opt-in
Also called double opt-in, DOI.
Last reviewed 11 October 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 both Google and Yahoo name 0.3 per cent as the level to stay under, with Google naming 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 is planned at 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 Single vs double opt-in: what each costs, and when, 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.
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