iCloud Private Relay on Mobile Networks: Performance Across Countries and Roaming

The growing adoption of privacy-oriented Internet services is reshaping how user traffic is handled and routed across the network. Among these services, Apple's iCloud Private Relay represents a large-scale deployment of a multi-party relay architecture, designed to improve user privacy while limiting the performance costs typically associated with additional network hops. Introduced in 2021 and integrated into Apple operating systems, the service provides users with an easy-to-use privacy-enhancing mechanism at a low cost, making its impact on Internet performance an important subject of study. In this work, we investigate the performance implications of iCloud Private Relay on mobile networks across different countries and usage scenarios. Through measurements performed on iPhones connected via cellular networks, we show that iCloud Private Relay reduces speed test throughput and increases latency, while its impact on web page load time is comparatively limited. We further analyze international roaming scenarios, where the interaction between home routing and the Private Relay overlay introduces additional complexity and can occasionally improve performance. Our results contribute to the understanding of large-scale, multi-hop privacy-enhancing architectures in mobile environments. To facilitate further research, we release our measurement dataset and software tools to the community.