There is a version of WhatsApp opt-in that maximises list size and a version that survives scrutiny. They are not the same flow, and after May 2027 the gap between them becomes a liability rather than a growth tactic.
Four flows, ranked
Weakest is the bundled checkout consent, where a single tick covers email, SMS and WhatsApp across service and marketing. It builds the biggest list and fails on granularity and purpose.
Next is the pre-selected toggle on a lead form. Better than bundled because it names the channel, still fails because consent has to be affirmative.
Strong is an unticked checkbox naming WhatsApp specifically, stating what you will send and roughly how often, with a link to a short purpose notice. Smaller list, defensible.
Strongest is double opt-in. The user ticks the box, then receives a WhatsApp message asking them to confirm, and only confirmed numbers enter the marketing list. Smallest list, highest engagement, and the only flow where you hold proof of intent inside WhatsApp itself.
Capture these fields at the moment of consent
- Timestamp with timezone
- Source URL or physical location of the form
- The exact purpose text shown to the user
- Notice version identifier
- Channel consented to, separately from other channels
- Confirmation timestamp if double opt-in
Store these in your own database, not only inside the BSP platform. Providers get switched, and consent history that lives only in a vendor is consent history you can lose during a migration.
The number people worry about
Teams resist the stronger flows because the list shrinks. It does, typically by a large margin when moving from bundled to double opt-in. What usually also happens is that delivery and read rates rise, block rates fall, and cost per conversion improves, because you stopped paying to message people who never wanted the messages.
Run it as a test rather than a leap of faith. Put the strong flow on half your traffic for a month and compare cost per conversion, not list growth.
General information, not legal advice. Rules current as of July 2026.