---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/content/session-definitions#article
headline: Session Definitions
description: Understand user-initiated and business-initiated WhatsApp sessions, approval needs, and how to use Twilio APIs for seamless messaging.
url: https://www.twilio.com/docs/content/session-definitions
inLanguage: en
dateModified: 2026-08-28T17:35:35.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# Session Definitions

## User-Initiated Session

A User-Initiated Session, also known as an In-Session conversation, is initiated by a user sending a message. After the recipient replies to a message or if the user is the first party to send a message, messages are considered in session for the next 24 hours. In-session messages don't always require WhatsApp approval. See the [WhatsApp Approval Requirements](#whatsapp-approval-requirements) table for details. Additionally, using the Content API for Facebook Messenger is only available for User-Initiated Sessions.

## Business-Initiated Sessions

A Business-Initiated Session, also known as an outbound or Out-of-Session conversation, is initiated by a company sending a message without the recipient first messaging them. By default, to send outbound messages to WhatsApp users, template approval by WhatsApp is required. This is done as a separate API request via the Content API. Business Initiated Sessions are only allowed on WhatsApp. Some content types aren't allowed to be outbound messages, such as list-picker and location.

## WhatsApp Approval Requirements

|                         | **WhatsApp Session Type**                                                                        |                                                                                       |
| ----------------------- | ------------------------------------------------------------------------------------------------ | ------------------------------------------------------------------------------------- |
| **Twilio Content Type** | **User Initiated: 24 hour customer service window** (initiated by inbound message)               | **Business Initiated: Out of Session** (initiated by a business - no inbound message) |
| twilio/text             | ✅ Can reply to inbound messages                                                                  | ⚠️ Template approval required to send outbound messages                               |
| twilio/media            | ✅ Can reply to inbound messages                                                                  | ⚠️ Template approval required to send outbound messages                               |
| twilio/location         | ✅ Can reply to inbound messages                                                                  | ❌ Not supported                                                                       |
| twilio/call-to-action   | ⚠️ Template approval may be required to reply to inbound messages based on buttons types present | ⚠️ Template approval required to send outbound messages                               |
| twilio/quick-reply      | ✅ Can reply to inbound messages                                                                  | ⚠️ Template approval required to send outbound messages                               |
| twilio/list-picker      | ✅ Can reply to inbound messages                                                                  | ❌ Not supported                                                                       |
| twilio/card             | ⚠️ Template approval may be required to reply to inbound messages based on buttons types present | ⚠️ Template approval required to send outbound messages                               |
| twilio/carousel         | ✅ Can reply to inbound messages                                                                  | ⚠️ Template Approval Required to send outbound messages                               |
| twilio/catalog          | ✅ Can reply to inbound messages                                                                  | ⚠️ Template Approval Required to send outbound messages                               |
| twilio/flows            | ⚠️ Template approval required to reply to inbound messages                                       | ⚠️ Template Approval Required to send outbound messages                               |
| whatsapp/card           | ⚠️ Template approval may be required to reply to inbound messages based on buttons types present | ⚠️ Template approval required to send outbound messages                               |
| whatsapp/authentication | ⚠️ Template approval required to reply to inbound messages                                       | ⚠️ Template approval required to send outbound messages                               |