Enhance the Pre-Chat Page for Snap-Ins Chat | Snap-Ins for Web Developer Guide

Pass Nonstandard Pre-Chat Details
Further control the pre-chat experience using parameters in your Snap-ins code snippet. Two parameters relate to the pre-chat experience: extraPrechatFormDetails and extraPrechatInfo. With these parameters, you can send information to the agent and to your org beyond what’s shown on the pre-chat form.

Pre-Chat Code Examples
The following examples illustrate some common use cases for pre-chat code snippets.

Route Chats Based on Pre-Chat Responses with Direct-to-Button Routing
Set your snap-in to route chats to different chat buttons based on the customer’s pre-chat response on any and all of your pre-chat fields. Available when you upgrade your code snippet to version 4.0.

Set Certain Pre-Chat Form Fields to Automatically Populate when Customers are Logged In
When your customers are logged in, you already know basic information like their name and email address. Use this array in your 4.0 code snippet to populate relevant pre-chat fields for them. You can mix and match fields for different record types. This information is for snap-ins that are placed outside of Salesforce with Lightning Out (beta). If you use your snap-in inside Communities, you can enable the contact fields to fill in automatically in the Snap-ins Chat component settings.