@Colony Creative Thanks for asking question!
To further elaborate here-
Azure App Service offers two kinds of SSL connections: SNI SSL Connections and IP Address SSL Connections. SNI-based SSL is compatible with modern browsers, whereas IP-based SSL functions across all browser types.
Utilizing SNI-based SSL incurs no extra cost. With Standard and Premium service plans, one IP SSL connection is included at no additional fee per App Service Plan.
You may want to know that SSL is not supported with Free and shared service plans.
But Additional SSL connections can be obtained for the following rates, with the SSL certificate itself requiring a separate purchase in all cases.
Please share more details on your usage if query remains.