This guide focuses on 1:1 messaging through the ChatWerk API — that is, sending messages directly to individual WhatsApp users.
In this context, WhatsApp enforces specific delivery rules, such as the 24-hour service window and the use of approved message templates.

If you intend to send messages to multiple recipients simultaneously (1:N messaging), we recommend using a Chatflow or the Broadcast feature instead. These tools are optimized for large-scale delivery, automation, and segmentation, and should be used rather than the direct 1:1 API endpoints described here.

The sections below explain how WhatsApp handles message delivery for individual contacts and outline the technical differences between Template Messages and Free-Form Messages.

Message Delivery Mechanisms
When sending messages to individual WhatsApp users, the API distinguishes between two message types: Template Messages and Free-Form Messages.
Each type follows its own delivery rules and constraints.

Message Call

A Free-Form Message is any text message, allowed anytime on all messengers and on WhatsApp only within 24 hours.

Template Call

A WhatsApp Template Message is a pre-approved message format that can be sent at any time.

Choosing the Right Message Type

Scenario	Recommended Message Type
First contact with a user	Template Call
Message outside 24-hour window	Template Call
Reply within 24-hour window	Message Call
Transactional notification	Template Call
Conversational reply	Message Call

Understanding and correctly applying these delivery mechanisms ensures that your messages are delivered successfully and remain compliant with WhatsApp’s platform policies.