Klaviyo SMS

Overview

Klaviyo SMS is the text messaging marketing channel within the Klaviyo platform, built specifically for e-commerce businesses on Shopify, WooCommerce, BigCommerce, and similar platforms. It enables brands to collect mobile phone numbers through website pop-ups and inline forms, then send targeted promotional texts and automated transactional messages based on customer behavior and purchase history. Klaviyo SMS operates alongside Klaviyo Email as a unified customer engagement platform with shared subscriber profiles and behavioral data.

What This Script Does

Form Rendering and Phone Number Capture

• Loads JavaScript from static.klaviyo.com and related Klaviyo CDN domains
• Renders phone number capture interfaces: modal pop-ups, flyouts, embedded inline forms, and teaser bars
• Captures the visitor's phone number and explicit SMS consent on form submission
• Submits phone number, consent timestamp, and consent language to Klaviyo's subscriber API
• Script file: https://static.klaviyo.com/onsite/js/klaviyo.js (same core script as Klaviyo Email)

Cookies Set

• __kla_id — Klaviyo's primary cross-session visitor identifier; base64-encoded JSON containing $anonymous and $exchange_id keys; first-party, persistent (2 years); links all browsing activity to a Klaviyo subscriber profile
• __kla_viewed_pages — tracks page view history within the session for triggering behavioral pop-ups
• __kla_ss — session identifier for Klaviyo's real-time personalization layer

Behavioral Tracking for SMS Automation

• Tracks page views (Viewed Product, Viewed Category) for browse abandonment SMS triggers
• Fires Added to Cart and Started Checkout events for cart abandonment SMS flows
• Monitors Placed Order and Fulfilled Order for post-purchase SMS sequences
• All events are piped into Klaviyo's customer profile, building a behavioral history used to trigger automated SMS messages

Attribution Tracking

• When recipients click links in SMS messages and land on the site, Klaviyo captures _kx URL parameters and utm_source=klaviyo parameters to attribute the visit to the originating campaign
• Click-through attribution creates a conversion record linking the SMS send to downstream purchases

Data Transmitted

• Visitor browsing events, cart activity, and purchase data sent to a.klaviyo.com API endpoints
• Phone numbers, consent records, and behavioral profiles stored on Klaviyo's US servers (AWS)
• Klaviyo participates in the EU-US Data Privacy Framework

Consent & Compliance

Consent category: Marketing

Klaviyo SMS is marketing technology. Under GDPR Article 6(1)(a) and Article 7, loading behavioral tracking scripts that build marketing profiles and enable targeted advertising requires explicit prior consent. The ePrivacy Directive requires consent for the __kla_id persistent cookie and the behavioral tracking scripts. Separately, SMS marketing in the EU requires explicit consent under ePrivacy Article 13 (direct electronic marketing) — this is a distinct consent from cookie consent. Under CCPA/CPRA, the behavioral data collected by Klaviyo (browsing history, cart activity, purchase patterns) linked to identifiable profiles constitutes "sharing" of personal information for targeted advertising, triggering "Do Not Sell or Share" opt-out obligations. Klaviyo must not load until valid marketing consent is obtained.

Should You Block This Without Consent?

Yes. Klaviyo SMS scripts track detailed browsing behavior, build persistent marketing profiles, and power targeted SMS advertising. Both the tracking cookies and the behavioral data collection require explicit marketing consent before the script loads.