James Rosewell

James Rosewell is a UK-based AdTech entrepreneur best known as the co-founder and CEO of Movement for an Open Web (MOW), an industry coalition that has become the leading organised voice opposing Google's Privacy Sandbox initiative. His work filing formal complaints with the UK Competition and Markets Authority (CMA) against Google's proposed cookieless transition has directly influenced regulatory scrutiny at the highest levels, contributing to the CMA's ongoing oversight commitments that Google accepted as binding conditions before proceeding with third-party cookie deprecation plans. Before founding MOW, Rosewell built his AdTech credentials as a technology entrepreneur, most notably as CEO of 51Degrees, a device detection and data intelligence company he founded and led for over a decade. This hands-on experience building AdTech infrastructure gave him deep technical grounding in the standards and protocols that underpin the open web's advertising ecosystem, which he has since channelled into advocacy and regulatory engagement. Rosewell is widely regarded as a standards-setter and industry watchdog in the AdTech space, engaging with bodies such as the W3C to challenge aspects of Privacy Sandbox proposals on technical and competitive grounds. His influence extends beyond the UK, with his complaints and arguments informing regulatory conversations in the EU and US about the market power implications of browser-led identity and targeting solutions.

Last updated Jun 11, 2026 by ATDb automated enrichment