Abstract—Web of Things (WoT) brings web technologies and knowledge graphs to Internet of Things. JSON-LD, with its popularity in representing and exchanging structured data on the web, can be a suitable data format for WoT. However, its verbose nature can pose challenges for constrained IoT devices with limited bandwidth, and memory. In this paper, we study CBOR-LD scheme for encoding JSON-LD to a lightweight binary format CBOR (Compact Binary Object Representation). We also study possible optimisations such as using a custom dictionary. We provide a C library and evaluate it on several examples. Results demonstrate that our approach provides savings up to 94% in terms of network overhead for IoT devices.