We build a system which works as software as a service. Now I am wondering if it is needed to give the version number to the clients. For example Facebook doesn't give a version number neither does Google. My question is basically would one include version numbers in an application where the client cannot change the version themselves? ## Update 1 Just a quick update, yes we do offer an API and the API will be versioned in a similar way like Atlassian does `api/` and then `api/v2/` and so on. The version number is just about the website the customer sees, not about developers. Internally we use Jira for project management and there we also use the Jira releases feature. So internally we do have version numbers. Just not for the customers at the moment.