Abstract : A Web configurator offers a highly interactive environment to assist users in customising sales products through the selection of configuration options. Our previous empirical study revealed that a significant number of configurators are suboptimal in reliability, efficiency, and maintainability, opening avenues for re-engineering support and methodologies. This paper presents a tool-supported reverse-engineering process to semi-automatically extract configuration-specific data from a legacy Web configurator. The extracted and structured data is stored in formal models (e.g., variability models) and can be used in a forward-engineering process to generate a customized interface with an underlying reliable reasoning engine. Two major components are presented: (1) a Web Wrapper that extracts structured configuration-specific data from unstructured or semi-structured Web pages of a configurator, and (2) a Web Crawler that explores the configuration space (i.e., all objects representing configuration-specific data) and simulates users' configuration actions. We describe variability data extraction patterns, used on top of the Wrapper and the Crawler to extract configuration data. Experimental results on five existing Web configurators show that the specification of a few variability patterns enable the identification of hundreds of options.