This book constitutes the refereed post-conference proceedings of the 6th IFIP International Cross-Domain Conference on Internet of Things, IFIPIoT 2023, held in Denton, TX, USA, in November 2023. The 36 full papers and 27 short papers presented were carefully reviewed and selected from 84 submissions. The papers offer insights into the latest innovations, challenges, and opportunities in IoT, covering a wide array of topics, including IoT architectures, security and privacy, data analytics, edge computing, and applications in various domains.