Online specialised free dictionaries offer assistance to everybody in need of information on the Web. More refined search tools are needed however in order to get as quickly as possible to the best terminological resource. At present Internet surfers can rely upon some lexicographical inventories and metasearch engines to acquire the information needed more easily. However, none of these resources offer evaluations of the collected vocabularies, or advice for a more efficient search. We present a critical inventory of 505 Web dictionaries, offering a broad overview of their main features. The analysis has been carried out using an evaluation form managed by a relational database (also published online) that assigns ratings and can also be used for analytical searches. The various fields of the form, and an adequate rating system allow us to define the specific parameters for three users’ profiles (layman, semi-expert, expert) and four kinds of situations (cognitive, communicative, translation, learning) which are used for a qualitative analysis of dictionaries backed up by quantitative assessments.