Data compression plays a pivotal role in the efficiency of decentralised web systems by reducing the size of data that needs to be transmitted across the network. In distributed networks, particularly those that are decentralised, data often needs to be sent between various nodes that may not always have high bandwidth connections. Compression techniques, both lossless and lossy, can significantly decrease the amount of data being transferred, thus reducing transmission times and bandwidth costs. Moreover, efficient compression algorithms can help in maintaining faster data exchanges, which is crucial for the performance of real-time applications within decentralised systems.

Decentralisation significantly impacts the scalability of distributed networks by allowing them to grow and adapt without the need for central oversight or control. In a decentralised network, new nodes can be added with relative ease, which means that the network can expand to accommodate increasing amounts of data and processing demands. This contrasts with centralised systems, where scaling up often involves significant investments in infrastructure and overhauling existing systems. The modular nature of decentralised networks means they can be scaled horizontally, adding more nodes as needed, which is a more cost-effective and flexible approach to scalability.

Decentralisation could profoundly affect the user experience on the web by improving data access speeds, enhancing privacy, and potentially offering more personalised content. Since decentralised networks store and process data across multiple nodes, users can often retrieve information from a node closer to their location, decreasing latency. Furthermore, a decentralised approach provides users with greater control over their data, potentially increasing privacy and security due to the lack of a centralised data store. However, the user experience may also face challenges, such as the need for more robust authentication methods to secure access to distributed services and ensuring a consistent experience across various nodes.

The decentralisation of hardware in distributed networks introduces several risks, including security vulnerabilities and the management of a more complex network topology. As the number of devices increases, so does the attack surface for potential cyber threats, making it more challenging to ensure consistent security protocols across all nodes. Additionally, decentralisation can complicate network management and data integrity, as there is a need for robust synchronisation mechanisms to ensure that all nodes have the most current and consistent data. These risks require sophisticated strategies and technologies to mitigate, ensuring the reliability and safety of distributed networks.

Advancements in IoT devices have propelled the decentralisation of the web by integrating countless new nodes into the network, each capable of generating and processing data. Modern IoT devices, equipped with enhanced computational abilities and connectivity, contribute to a distributed network's data pool, facilitating complex tasks such as real-time analytics and decision-making at the edge of the network. This reduces the dependency on centralised data centres and disperses data processing capabilities geographically, which aligns with the principles of a decentralised web—promoting efficiency, privacy, and a more evenly distributed network load.