We present contextual facets, a novel user interface technique for navigating websites that publish large collections of semi-structured data. Contextual facets extend traditional faceted navigation techniques by transforming webpage elements into user interface components for filtering and retrieving related webpages. To investigate users’ reactions to contextual facets, we built FacetPatch, a web browser that automatically generates contextual facet interfaces. As the user browses the web, FacetPatch automatically extracts semi-structured data from collections of webpages and overlays contextual facets on top of the current page. Participants in an exploratory user evaluation of FacetPatch were enthusiastic about contextual facets and often preferred them to an existing, familiar faceted navigation interface. We discuss how we improved the design of contextual facets and FacetPatch based on the results of this study.