Computer Configuration > Administrative Templates > Microsoft Edge - Default Settings (users can override) > Content settings
Both
HKLM\Software\Policies\Microsoft\Edge\Recommended
Set this policy (recommended only) to register a list of protocol handlers. This list is merged with ones registered by the user and both are available to use. To register a protocol handler: - Set the protocol property to the scheme (for example, "mailto") - Set the URL property to the URL property of the application that handlers the scheme specified in the "protocol" field. The pattern can include a "%s" placeholder, which the handled URL replaces. Users can't remove a protocol handler registered by this policy. However, they can install a new default protocol handler to override the existing protocol handlers. Example value: [ { "default": true, "protocol": "mailto", "url": "https://mail.contoso.com/mail/?extsrc=mailto&url=%s" } ]