Carbohydrate active-enzymes are responsible for the degradation and synthesis of oligo- and polysaccharides. Evolved in parallel with the use and creation of new carbohydrates, they can now be classified in sequence/structure-related enzymes families, often presenting different activities, but sharing a fold and common catalytic machinery. Their core can be designated as a catalytic module. CAZyModO, a WWW server dedicated to the family classification and modular description of these enzymes, will be presented The server provides a full perspective of the modularity of these enzymes. Glycosidases have been known to exhibit ancillary modules that facilitate binding and degradation of unsoluble saccharides. These modules are now classified into families. The increasing use of these modules in biotechnological applications requires a better knowledge of extent of protein modularity, especially following the advent of genomic data. Modularity can have a different impact on protein stability depending if modules are juxtaposed and therefore dependent, or appart with functionally independent modules connected by linkers. The understanding of modular architecture is essential for enzyme engineering.