In this age of information technology, the Internet of Things (IoT) is one of the most promising technologies. The Internet of Things (IoT) allows pervasive data gathering and network connections, bringing substantial and essential convenience and insight to both everyday living and industrial processes. However, IoT continues to face a lot of difficulties and is exhibiting a number of concerns that must be solved immediately. Counterfeit hardware, software flaws, communication security problems, system administration challenges, and data privacy concerns are all major concerns with today's IoT infrastructure. In the mean time, due of its decentralization, receptiveness, and security, blockchain has provoked public consideration and showed extraordinary potential as a developing data innovation. A portion of the previously mentioned inadequacies can be addressed by utilizing blockchain to an IoT climate, while a portion of the previously mentioned shortcomings can be addressed by applying blockchain to an IoT biological system. The objective of this article is to present blockchain's utilization in IoT applications. We talk about the numerous challenges that an IoT framework faces, as well as the benefits of consolidating blockchain into IoT foundation. We for the most part focus on exhibiting blockchain applications in the IoT with further developed capacities and security. We additionally address cutoff points and future possibilities to reveal insight into blockchain in IoT research.