There’s a pressing need for protecting digital library (DL) collections since digital objects can be easily copied, edited, and redistributed. Digital content protection is thus attracting attention. In this paper, we propose a peer-to-peer approach to collaborative Web image copy detection for protecting DL collections, which is helpful to public libraries with limited resources. We design a collaborative framework that incorporates multiple peers to share the loads of crawling and copy detection tasks. It facilitates better utilization of limited network and computing resources. Our experiment results demonstrate the efficacy and potential of the proposed approach. Further investigation is needed to verify its scalability.