In this paper we address the process of developing a European Standard on Animal Welfare. We look at this process as an intervention in the messiness of the labels and brands that make claims about the quality of life of farm animals, currently proliferating in Europe, and as an interference in the ordering of the specific practices of animal farming, by defining new goals, values, competences and by affecting the forms of organisation of these practices. In the first part of the paper we will describe how the problem of increasing the welfare of farm animals in Europe has been translated in the EU Commission into the political issue of increasing the ‘transparency’ of the market for animal foods within the European Union, to increase ‘consumers information’ about the ethical status of the animal products available on the market and to facilitate ‘consumers’ choice’ according to the preferred level of animal welfare. Then we will describe the development of the tool that has been chosen in order to address this issue: the EU animal welfare standard based on animal welfare science and developed through a dedicated VI Framework research project called Welfare Quality. Finally we will try to address the question of how much flexibility and attention to specific conditions can be built into such a standard for making it a fluid technology, a tool that can work in different locations and that maintains an attentiveness to diversities and to a rich and multiple definitions of quality of life of animals as we find in the varied human- animals societies and animal farming practices in Europe.