Unable to Access Salesforce Survey as Guest User – Merge Field Permission Error

Root Cause

This issue occurs because of how Salesforce Surveys handle merge fields. When a survey is created with merge fields, Salesforce automatically generates a Flow that retrieves merge field values by querying the Survey Subject object. The Guest User profile — which executes the Flow for unauthenticated users — does not have permission to access this object or its related objects, causing the Flow to fail and preventing the survey from loading.

Steps to Fix – Update Merge Field Variables Setting

To allow Guest Users to access Salesforce Surveys sent via email when merge fields are used, update the Merge Field Variables setting to use System Context (which ignores record-level access):

1. Navigate to the affected survey in Salesforce.
2. Click Open Latest Version.
3. If the survey is currently activated, go to the View tab and select Create New Version from the dropdown menu in the top-right corner.
4. Open Advanced Settings and click Merge Field Variables.
5. Set Merge Field Variables to System Context – Ignore record-level access.
6. Save and activate the survey.

After applying these changes, Guest Users can access survey links sent via email without encountering access errors.