To ensure that additional branding works even for an external site through the Messaging In-App and Web(MIAW) Embedded Service Deployment, we need to modify the Static Resource URLs.
This Article : https://help.salesforce.com/s/articleView?id=000395566&type=1 can be followed if the sites were built using Aura FrameWork Template.
As the Experience sites that get auto-created for Messaging In-App and Web deployments are Lightning Web Runtime FrameWork, the steps from above article will fail.
Follow the below steps to construct the correct URLs for using the static resource with Embedded Service Deployments (ESW) for MIAW :
Go to Setup -> Sites.
Locate the URL of the site that corresponds to the Site Endpoint configured on your MIAW embedded service deployment.
Copy the entire Site Endpoint URL.
Example Endpoint: https://domain.my.site.com/ESWTest1748430915517
Go to Setup -> Static Resources.
Open the required Static Resource.
Click the View file button.
Copy the URL path that appears after your domain (e.g., after .com).
Example Path: /resource/1759825368000/Agent_Icon
The Static Resource URL must be constructed using the following specific syntax for ESW/MIAW to correctly locate the file within the site structure:
Syntax: [Site Endpoint URL] + /sfsites/c + [Static Resource Path]
Final Constructed URL Example:
https://domain.my.site.com/ESWTest1748430915517/sfsites/c/resource/1759825368000/Agent_Icon
Link to product documentation: Branding Elements Guide for Enhanced Chat
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