UX Improvement: Clarify 'Custom domain on other DNS' option for cross-subscription Azure DNS zones

[Jenp-AICraftWorks]

Description

The custom domain configuration UI in Azure Static Web Apps has confusing labeling that creates friction for users with Azure DNS zones in different subscriptions.

Current Behavior

When adding a custom domain to a Static Web App, users are presented with two options:

• Custom domain on Azure DNS
• Custom domain on other DNS

The 'Custom domain on Azure DNS' option only shows DNS zones in the same subscription as the Static Web App. If a user's DNS zone is in a different Azure subscription (common in multi-subscription architectures), it won't appear in the dropdown.

The label 'Custom domain on other DNS' implies it's only for external DNS providers (GoDaddy, Cloudflare, etc.), leading users to believe it won't work for Azure DNS zones in other subscriptions.

Issue

Users naturally select 'Custom domain on Azure DNS' when their DNS is hosted on Azure, then become confused when their DNS zone doesn't appear. This creates unnecessary support burden and delays in configuration.

Expected Behavior

The UI should clearly indicate that cross-subscription Azure DNS zones require the 'other DNS' option.

Suggested Solutions

Option 1: Update Label (Preferred)

Change 'Custom domain on other DNS' to:
'Custom domain on other DNS or in other Azure Subscription'

Option 2: Add Helper Text

Add explanatory text under 'Custom domain on Azure DNS':

'Only shows DNS zones in the current subscription. For DNS zones in other subscriptions, use "Custom domain on other DNS".'

Option 3: Dynamic Detection

Detect when users have DNS Zone Contributor permissions on zones in other subscriptions and show those zones in the dropdown with a subscription indicator.

Impact

This affects organizations using:

• Multi-subscription strategies (dev/staging/prod separation)
• Centralized DNS zone management
• Enterprise governance models with subscription-based isolation

Reproduction Steps

1. Create Static Web App in Subscription A
2. Host DNS zone in Subscription B
3. Grant Static Web App's managed identity 'DNS Zone Contributor' role on DNS zone in Subscription B
4. Attempt to add custom domain in Azure Portal
5. Select 'Custom domain on Azure DNS' - DNS zone doesn't appear
6. User confusion ensues

Environment

• Azure Portal: Current version (November 2025)
• Resource: Azure Static Web Apps
• Feature: Custom Domains configuration UI
• Scenario: Cross-subscription Azure DNS zone

Additional Context

The functionality works correctly when using 'Custom domain on other DNS' - the managed identity permissions allow automatic validation. The issue is purely UX/labeling that doesn't reflect this capability.

Cross-subscription scenarios are increasingly common as organizations adopt Azure landing zone patterns and multi-subscription governance models.

---

Thank you for considering this improvement! Happy to provide additional details or test any UX changes.