To understand the history of an extraordinary librarian fund, considered «among the most coherent of the Italian humanism» and substantially come to our days as a whole, it is absolutely necessary to follow the education years and reconstruct the carrier steps of Guarnerio d’Artegna, borne either in Portogruaro or Zoppola around the year 1410 in a family who had once had the Artegna castle in fief by the patriarchs. Only a hint is here given at the school he attended in the patriarchate, the Roman experience as a familiar to cardinal Antonio Pancera, former patriarch of Aquileia (1427/28-1431), his participation, briefly though, in the Ferrara-Florence Council (1438-1439), his friendship with some Friulian people in the pontifical court retinue (Bartolomeo Baldana and Giacomo di Giacomo da Udine), his canonries of Aquileia and Udine, his appointment as a vicar of the patriarch Ludovico Trevisan (1445-1454), his parish rectory at San Daniele del Friuli, his narrow relations with the Friulian master-teachers of the time. The plan to form the library he would have left in legacy to the community of San Daniele in 1466, though it had roots in a distant time, was only fulfilled when he was in charge as a patriarchal vicar, for at that time he could dispose of relevant financial resources for the purchase of materials, the payment of copyists and illuminators, the travels possibly needed time by time. Particularly relevant from the cultural viewpoint were Guarnerio’s relations with Francesco Barbaro and Ludovico Foscarini, General Governors (‘luogotenenti’) of the ‘Patria del Friuli’, from one side, and with Giovanni da Spilimbergo and Francesco Diana, rectors of the school of Udine, who put him in touch with the main centres of the Venetian and Florentine humanism and provided him with their students as copyists (among others Giovanni Belgrado, Nicolò de Collibus, Marco di Giovanni da Spilimbergo). Guarnerio made in fact use of only one professional copyist: Battista da Cingoli. As to decorations, in the years of his vicariate Guarnerio’s collection was enriched by luxurious features. Giordana Mariani Canova has remarked that only a few codices show a modern-fashioned decoration (‘alla moderna’), characterized by late-Gothic elements. The majority of Guarnerio’s codices are distinguished by the antique-fashioned decoration (‘all’antica’) inspired to that taste Humanism esteemed as characteristic of the Classical Age handwritten books: with the Florentine-styled white vine-stem borders (the so-called ‘bianchi girari’) or, more originally, in form of a tied neck-knot (‘a cappio annodato’). The tied neck-knot motif, which finds its first example in the ms. Guarneriano 8, was drawn as an imitation of early-medieval ribbon-knotted decorations, known in Paduan and Venetian milieus; it is therefore possible that some codices were decorated in Padua or Venice in accordance with the common practice to send manuscripts to those centres where renowned illuminators worked. Guarnerio’s codices are among the first witnesses of such a kind of decoration that was then spread in various centres of Northern Italy in the second half of the fifteenth century. For this reason «Guarnerio’s experience is undoubtedly to be considered the basis for the development of one of the most learned and refined threads of the humanistic decoration».