Photography is an important social document for the study of the nineteenth and twentieth centuries, promoting the dissemination, conservation and valorization of political, social, scientific and cultural activities of man. Its polysemous and subjective nature has made it difficult to implement common policies and procedures concerning its description and recovery. The emergence of web 2.0 provides new ways of publishing, sharing and organizing information online. Folksonomy thus emerges as an interactive and inclusive resource for representing these contents through the users free language. In this context, it is theorized that the use of folksonomy could be applied and would be useful, in some circumstances, in the treatment of photographic images. The main goal is to analyze which contributions folksonomy brings to the indexation processes of photographic documents coming from public archives, in order to preserve and share this heritage. The adopted methodology consisted, at first, in a systematic exploration of folksonomy in archival context and applied to photographic documentation, to identify scientific works in online repositories and databases. At the same time, an online collection of photographs was created on Flickr, belonging to the David Freitas Collection of the Photographic Archive of Évora City Hall, on which social indexing actions will be promoted. The practical study carried out will contribute to ascertain why systems that allow social indexing features are important to institutions holding photograph collections.