---
schema_version: "1"
id: 4b4665674fd592a08922e8d5c26525e3ea98d9a4bb58227634adbac462d919b0
title: Understand the previewData Object
collection: admin
version: current
locale: en-us
portal_url: https://docs.salesforce.com/admin/current/en-us/mktg/264-0-0/mktg_content_understand_the_previewdata_object.md
canonical_url: https://help.salesforce.com/s/articleView?id=mktg.mktg_content_understand_the_previewdata_object.htm&release=264.0.0&type=5
source_site: help.salesforce.com
content_type: documentation
content_hash: 7930406691f8ada62ebfa3903ef7848aa76974217327b1bb38547b2e7a5c8e53
description: Your custom LWC receives a previewData object that contains contextual information about the message being previewed. The fields available in previewData vary by channel.
products:
  - Marketing
release: "264"
---
# Understand the previewData Object

Your custom LWC receives a previewData object that contains contextual information about the message being previewed. The fields available in previewData vary by channel.

## Email

 
| Field | Description |
| --- | --- |
| `channelType` | The type of channel for the message, for example, Email |
| `content` | The rendered HTML body of the email |
| `contentKey` | A unique identifier for the content record |
| `emailSubject` | The subject line of the email |
| `emailPreheader` | The preheader text of the email |

## SMS and WhatsApp

 
| Field | Description |
| --- | --- |
| `channelType` | The type of channel for the message, for example SMS or WhatsApp |
| `content` | The rendered text body of the message |
| `contentKey` | A unique identifier for the content record |

When a recipient is selected from a segment, `previewData` is personalized and merge fields are populated with that member's data. When no recipient is selected, `previewData` contains content that isn’t personalized.

## UiPreviewMessageTabDef Field Reference

   
| Field | Description | Constraints | Example |
| --- | --- | --- | --- |
| `Id` | A unique identifier for the record | Populated automatically when you save | (auto-generated) |
| `DeveloperName` | The API name of the tab definition | Must start with a letter. Can contain only letters, numbers, and underscores. Must not contain spaces, end with an underscore, or contain two consecutive underscores. | Example\_CustomTab |
| `TabName` | The label that appears on the tab in the Preview and Test modal | — | Custom Tab |
| `IsActive` | Determines whether the tab appears in the Preview and Test modal | Customers who install the UiPreviewMessageTabDef package can modify this field | true |
| `SupportedChannel` | The channel where this tab is relevant | Valid values: Email, SMS, WhatsApp | Email |
| `LightningComponentDefId` | The ID of the LightningComponentBundle that provides the tab content | Must be an 18-character Salesforce ID | 18-character ID from your LWC |