Hello P.J. van Beuzekom,

Importing a v11 project into version 12 will automatically convert it to v12 format.  This will then render it unable to be opened in v11.

So by definition if you buy v12 and use it to create websites for your customers, then your customers must also have a copy of v12 if they want to edit the project you've created for them on their own computer.

There is, of course, nothing to stop you continuing to use version 11 for those clients who do not wish to upgrade to version 12, as your WebSite X5 licence is perpetual and will not expire.

Kind regards,

Paul