Actors are stakeholders involved in brownfield revitalization processes who assume an active role in channelling these processes based on their goals and means. This report distinguishes three categories of actors: primary actors, who are the principal addressees of the Timbre tools because they are involved in the regeneration of specific sites on a full-time basis; secondary actors are also involved in brownfield regeneration and they are also addressees of Timbre, even if their focus typically extends beyond the revitalization of a specific site while their interests can be convergent or divergent with those of the primary actors; and veto players who have decision-making power to foster or block brownfield revitalization, but largely from outside the brownfield market itself. In this sense, veto players are animated by political and/or economic interests, which Timbre researchers can (and should) take into account but which they cannot effectively influence through their research activities and outcomes (i.e. Timbre tools or approaches).