Definition
Double opt-in is a two-step sign-up in which a person first enters their phone number and then confirms it, for example by replying to a code or tapping a link, so the business can prove who consented.
A typed-in number could belong to someone else, so a single checkbox leaves you unable to show who actually entered it. Double opt-in closes that gap: after the first step the person receives a message and confirms by replying or tapping a link, which proves control of the number.
It matters most where consent must be provable. In Germany, section 7(2) no. 2 UWG treats advertising by electronic means without prior express consent as an unreasonable nuisance, and the GDPR requires consent to be freely given, specific, informed and unambiguous. The law asks for provable consent, not a particular method, and double opt-in is the common way to prove it. Our regulation data lists it as the operator-preferred standard for marketing in Germany and the UK.
Log the consent source, wording shown, timestamp and channel for each recipient, and the time of the confirmation. Section 7(3) UWG contains a narrow exception for existing customers, but it is worded for email addresses and commentary disagrees on whether it covers SMS, so do not rely on it.
This entry is general information, not legal advice; have counsel review your sign-up flow. Our opt-in consent generator drafts sign-up and confirmation wording.
Frequently asked questions
Is double opt-in required by law in Germany?
The law asks for provable consent, not a particular method. Double opt-in is the common way to prove it, and our regulation data lists it as the operator-preferred standard. A checkbox alone leaves you unable to show who entered the number.
What does the confirmation step look like?
The person enters their number, receives a message, and confirms by replying with a keyword or code, or by tapping a link. The confirmation time is stored alongside the original consent record.
Is double opt-in the same as opt-in confirmation?
Not exactly. A confirmation message after a single opt-in tells the person they are subscribed, while double opt-in requires the person to act on that message before any marketing is sent.