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Summer '25: Redirect legacy (non-enhanced) My Domain hostnames update

Publish Date: May 7, 2026
Description

With the Summer '25 release, the setting "Redirect legacy (non-enhanced) My Domain hostnames" in My Domain Setup has been disabled. This change is part of Salesforce's preparation for the end of redirections for non-enhanced domains.
When this setting is disabled, legacy non-enhanced force.com site URLs no longer automatically resolve to the org's enhanced domain (*.my.site.com or *.my.salesforce.com), resulting in 404 errors for users or integrations still using the old URLs.
For organizations using legacy LiveAgent or Chat deployments, users may also encounter the following error in the browser console when attempting to initiate a chat session:

CORS Error: blocked by CORS policy — No 'Access-Control-Allow-Origin' header is present on the requested resource

This CORS error occurs because the aura_prod.js file is loaded from the legacy force.com domain in the chat deployment code on the third-party site. The legacy domain performs a redirect to the new enhanced domain but does not set the required CORS headers, causing the browser to block the request and prevent the chat from launching.

Resolution

Temporary Workaround: Re-Enable the Legacy Redirect Setting

As a temporary workaround, re-enable "Redirect legacy (non-enhanced) My Domain hostnames" in My Domain Setup (Setup > My Domain > My Domain Settings).
Only use this as a temporary measure. Ensure that end users and stakeholders are informed that the affected legacy URLs will no longer be supported after the Spring '26 major release, at which point this redirect setting will be permanently removed.

Additional Workarounds for Chat (Legacy LiveAgent)

Use one of the following options in conjunction with re-enabling the legacy redirect setting to resolve the CORS issue for Chat:

Option 1: Enable Lightning CDN

Enable "Enable content delivery network (CDN) for Lightning Component Framework" via Setup > Session Settings.
When Lightning CDN is enabled, Salesforce loads the aura_prod.js file from the CDN rather than from the legacy force.com site domain. This eliminates the CORS issue caused by the redirect from the legacy domain to the enhanced domain without CORS headers.

Important: Review the considerations in Enable the Lightning CDN to Load Applications Faster before enabling CDN in your org.

Option 2: Update Chat Deployment URLs

Update your chat deployment on your third-party site to use current, non-legacy URL references:

  • Update your chat deployment to use the latest version available for your org, OR
  • Replace or update all deployment references that currently use *.force.com site URLs to use *.my.site.com URLs for your Experience sites.

This eliminates the root cause by removing the dependency on the legacy force.com domain entirely.

Additional Resources
Knowledge Article Number

005036916

 
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Salesforce Help | Article