Prerelease versions of software and services are typically identified as Product Name Preview (preferred) or Code Name Preview.
In generic references, lowercase preview.
Avoid using beta to refer to a prerelease product that's ready for unstructured testing by customers. Use preview instead.
Examples
Office 2016 Preview
Windows 10 Insider Preview
Microsoft Power BI Preview
A preview of Azure Container Service is available.
See also sample vs. preview