Abstract : The Web of Things (WoT) relies on Web standards to enable interoperability between physical objects (things) and build applications using them. While most approaches (Cyber-Physical Systems, Internet of Things) require complex domain-driven software design that combines different disciplines such as electronics, networks and computing, we believe that generic solutions are needed to support WoT applications across the variety of things and application domains. To this end, we propose the notion of avatar as a Web-compliant software extension of a thing. Avatars achieve interoperability between things using semantic technologies and expose high-level functionalities as RESTful resources. They can collaborate with other avatars and form standard-compliant WoT applications that match end-users’ needs. We detail the notion of avatar and describe how avatar-based WoT infrastructures can improve the quality of Web of Things applications. We show how their architecture allows avatars to embed advances in different areas, and focus on contributions at different levels: tolerance to network disconnection, contextual adaptation and multi-agent negotiation.