If you are looking to expand into WhatsApp marketing, you do not need to reinvent the wheel. Klaviyo allows you to collect consent for both SMS and WhatsApp simultaneously, meaning you do not have to split your audience across multiple conflicting forms.
The mechanics are straightforward once you know which toggles to flip. Here is how to update your pop-ups, build dedicated capture pages, and pull existing email subscribers into your WhatsApp channel.
Capturing Dual Consent on Existing Pop-ups
If you already have a pop-up running to collect SMS numbers from existing email subscribers, you can repurpose that exact form. You do not need to build a separate pop-up just for WhatsApp. Doing that only adds friction and clutters your store.
Open your existing SMS form in the Klaviyo editor and click directly on the phone number input block. Under the channel dropdown, you will see options for text message, WhatsApp, WhatsApp and text message, and phone number only. Switch this setting to WhatsApp and text message.
With that single change, anyone submitting their mobile number opts into both SMS and WhatsApp at the same time. It is clean, efficient, and saves you from managing duplicate forms across your store.
Sorting Your Legal Disclosure and Compliance
When you collect mobile consent, compliance is non-negotiable. Klaviyo makes the technical side easy, but you still need to ensure your legal text is completely accurate.
Inside the form editor, locate the company name field in the compliance text block. You must insert your registered legal entity name here, such as In-box Email Marketing Limited, rather than just a casual trading name. Legally, you have to do this.
Make sure you also link directly to your terms of service and privacy policy within that block. Cutting corners on compliance text is a mistake. It takes roughly two minutes to set up properly and protects your sender reputation from day one.
The Checkout Opt-in Limitation
Here is the thing: right now, Klaviyo does not provide a direct method to capture WhatsApp consent at Shopify checkout through the standard integration. You can capture SMS consent at checkout, but WhatsApp is currently restricted to on-site forms and embedded pages.
It is an annoying platform limitation, but it is not a deal-breaker. It simply means your on-site sign-up forms and email retention campaigns need to do the heavy lifting.
Building a Dedicated Landing Page
To turn your existing email list into WhatsApp subscribers, create a dedicated opt-in page on your website. This works on Shopify, WordPress, or whatever CMS you run.
Create an embedded form in Klaviyo linked to your main WhatsApp subscriber list. Add a phone number block, set the channel to WhatsApp and text message, and remove the email field entirely. Add an incentive in the copy, such as offering a 20% discount code on the success step, and publish the form.
Next, embed that form code directly into a clean, blank landing page on your site. You now have a standalone destination URL specifically built to collect WhatsApp numbers from traffic you already own.
Using Universal Blocks in Your Email Campaigns
Once your landing page is live, you want to drive your existing email database to it. Create a clean content block in your email template with a clear call to action, inviting subscribers to join your WhatsApp VIP list for exclusive drops or discounts.
Link that button directly to your newly created landing page. Once you have built and styled the block, save it as a universal content block inside Klaviyo.
Drop that universal block into your core automated flows and your regular campaign sends. It acts as an ongoing passive funnel, steadily converting single-channel email contacts into high-intent mobile subscribers across every send.
Final Thoughts
Capturing WhatsApp consent in Klaviyo does not require a complex tech stack. Switch your existing mobile forms to capture dual consent, host an embedded form on a clean landing page, and use universal blocks to cross-pollinate your email list. Focus on getting the legal disclosures right before you start sending.
If you want help setting up high-converting sign-up forms and building a compliant mobile database, take a look at our Sign-up Forms service to see how we can optimise your capture strategy.
