This paper aims to describe users' tagging behavior in catalogues and in Flickr. Six platforms of two institutions and one consortium are analyzed: the main catalogue Discovery and Flickr page of the National Archives of the United Kingdom, the main catalogue Explore, the catalogue Archives and Manuscripts and Flickr page of the British Library, and the consortial search engine of the pan-European eBooks on Demand Library Network. The results of the document and user data analysis point to differences between archival and library collections, between catalogues and Flickr, illustrate the impact of different authorization and procedural rules, and confirm previous studies as regards to the small size of the active user group. Based on the data analysis, we offer eight recommendations for social tagging in libraries and archives concerning the issues of interface functionality and management, data collection, reflection of tags and maintaining the community.