Salesforce Enhanced Domains Spring 23 Enforcement

Enhanced domains are required for sandboxes and non-production orgs in Winter ’23 unless you enable an org-level setting that postpones their enforcement until Spring ’23.

When you enable enhanced domains, login URLs for your sites change. Your My Domain login URL changes when you enable enhanced domains in a sandbox. Enhanced domains don’t change your My Domain login URL in production unless you also change your My Domain name or suffix. 

When you enable enhanced domains, all URLs across your org contain your company-specific My Domain name, including Experience Cloud sites and Salesforce sites. Also, your URLs don’t change when your org is moved to another Salesforce instance.

Differences Between Sandbox and Production

When you enable enhanced domains, your production My Domain login URL format, MyDomainName.my.salesforce.com, doesn’t change unless you also change your My Domain name. However, enabling enhanced domains in a sandbox adds the word “sandbox” to the org’s My Domain login URL: MyDomainName--SandboxName.sandbox.my.salesforce.com.

 Potential Impact

• Users can experience errors when attempting to access Salesforce, including but not limited to Experience Cloud sites, Salesforce Sites, and Visualforce pages.
• Some embedded content stored in Salesforce no longer appears.
• Third-party applications can lose access to your data.
• Single sign-on integrations with sandboxes can fail.
• Single sign-on integrations with orgs using the *.cloudforce.com and *.database.com domain suffixes can fail.

https://help.salesforce.com/s/articleView?id=sf.domain_name_enhanced_why.htm&type=5