This is the first article to show that French public Open Data system can be given the legal status of a "service public". It stresses the differences between Open Data as an administrative policy, and Open Government. Most of the French policy achievements in the field of Open Data have emerged within the context of public service activities. Above all, the realisation of the existence of public data has led to the introduction of pragmatic reforms. Administrative jurisprudence has recognised that providing and publishing legal documents is a public service. In keeping with this principle, government departments also provide documents, statistical data and reports free of charge, a development that constitutes an unprecedented regime of transparency in public affairs. The multiple consequences of the public service status of French Open Data system are discussed and assessed. Some may relate to operating principles such as guarantees to users, including the protection of personal data. There are significant and in some ways fundamental differences between the English and French understanding of some terms and concepts employed in this article, notably "service public" and "public service", "interet general" and "public interest". This article was not written from a comparative law perspective, so it was felt that a simple English translation of this term was not appropriate. We have therefore in many cases retained the original French term.