OTT Messaging Apps
OTT (over-the-top) messaging apps deliver conversational messages within specific platform ecosystems rather than over the carrier SMS infrastructure. WhatsApp, LINE, KakaoTalk, WeChat, and RCS are the primary channels in this category.
Geography and penetration
OTT messaging adoption is strongly geography-driven:
- WhatsApp — dominant in EMEA, LatAm, South Asia; >2 billion monthly active users globally. Primary customer communication channel for retail and financial services in these markets.
- LINE — dominant in Japan and parts of Southeast Asia (Thailand, Taiwan). Business messaging requires a LINE Official Account and the LINE Messaging API.
- KakaoTalk — dominant in South Korea. Business messaging requires a KakaoTalk Business Account and Kakao i Open Builder or API access.
- RCS — a carrier-level rich messaging protocol (SMS successor) available via Google Messages and Samsung Messages on Android. Supports images, carousels, and quick-reply buttons at SMS-tier ubiquity (no app install required beyond Messages app) where carriers have enabled it.
How it differs from SMS and push
modality.sms is carrier-based plain-text messaging with near-universal reach at the device level; OTT messaging apps require the user to have installed and opted into a specific platform. modality.push is device OS-level and tied to app installs (the brand's app, not a platform messaging app). OTT messaging apps require the user to have an account on the specific platform.
CDP activation pattern
CDP activation to OTT messaging channels is a two-layer pattern:
- The CDW computes the target audience (e.g., all customers with WhatsApp opt-in flag = true AND lapse risk score > 0.7).
- A customer engagement platform or messaging API provider (Braze, Salesforce Marketing Cloud, Vonage, Infobip, Twilio) holds the platform-specific API credentials and message templates, receives the audience from the CDP or CDW, and orchestrates delivery.
Direct CDW-to-WhatsApp API calls without a CEP intermediary are technically possible (Meta's Cloud API supports direct POST) but operationally uncommon at scale — template compliance and rate-limit management typically justify the CEP layer.
WhatsApp technical specifics
WhatsApp's messaging policy divides business messages into four categories with distinct compliance requirements:
- Service messages (session messages) — within the 24-hour customer care window, free-form messages (text, images, audio, video, interactive buttons, carousels) are permitted without template pre-approval.
- Marketing messages — template-based; require explicit consumer opt-in consent independent of the 24-hour window. Template content must be pre-approved by Meta. Promotions, coupons, and re-engagement messages fall in this category.
- Authentication messages — autofill, zero-tap, and code-copy verification messages. Separate template category with streamlined approval.
- Utility messages — transactional templates (order updates, shipping notifications, appointment reminders). Require pre-approval but face lower scrutiny than marketing templates.
API layer. The Meta Cloud API (Meta-hosted) is the current recommended integration path for direct API access. Business Solution Providers (BSPs — Twilio, Vonage, Infobip, and others) offer managed API access, message orchestration, and compliance tooling on top of the Cloud API. For CDP activation, most CEPs (Braze, Salesforce Marketing Cloud) integrate via either the Meta Cloud API directly or through a BSP intermediary.
24-hour window and win-back implications. CDP win-back and lapse-reactivation campaigns target users who have not recently engaged — typically outside the 24-hour customer care window. This means the outbound message must be a pre-approved marketing template, not free-form. The template pre-approval lead time and explicit opt-in requirement make WhatsApp win-back campaigns meaningfully more complex to set up than email or SMS equivalents. See constraint.whatsapp-24h-messaging-window for the full constraint specification.