Manufacturers of all business areas are faced with growing customer demands and the corresponding complexity of their products. The need to offer highly customized variants becomes obvious for example in the automotive industry: innovative cars with configurable features move customers to buy newer models in increasingly shorter intervals. However, the costs are expected to be nearly stable from the customer's perspective. An industry approved approach to systematical design customizable products at reasonable costs are multivariant product lines: product line engineers compose models describing common and distinctive product features as well as logical constraints. Subsequently these models can be analyzed and optimized. In this paper, we present a free variant management tool called Glencoe. Glencoe is a web application developed and hosted at Trier University of Applied Sciences. Therefore, it is not necessary to install any software; it is accessible from any computer or mobile device. Glencoe allows the user to specify and visualize feature models using different views which emphasize specific aspects. The application is connected to several well-known and freely available theorem provers and SAT solvers. Thus, the user is able to analyze the product line for consistency, the number of product configurations and the existence of dead features. A set of metrics helps to evaluate the product line healthiness. Glencoe is intuitive to use since it is built according to state-of-the-art user interaction paradigms originating from mobile application development. As a rapid prototyping tool, it allows beginners as well as experts to build and analyze product lines.