After the fall of the Western Roman Empire the art of glassmaking underwent a decline in Europe, while in the Byzantine Empire and various regions of the near and far East, important glassmaking traditions were developed.
Byzantine glassmaking is not highly documented and opinions clash. There is no doubt however that glassmakers in Constantinople, Greece and other parts of the Byzantine Empire, produced both glass for daily use and objects of exceptional refinement. The most famous group of Byzantine glass is that of blown, decorated with gold and enamel, including the exceptional dark red glass bowl with silver gilt mount (10th-11th century), which has been in the Treasure in San Marco in Venice since 1204.

Important pre-Islamic glassmaking was developed in Persia and Mesopotamia under the Sassanian emperors (247-645) and was characterised by deeply faceted thick glass, often a bee-hive motif, or with various geometrical motifs. This technique may have derived from the combination of a very old local tradition of hard stone cutting, dating back to the Achemenide period, with the Roman faceted glass tradition.

Islamic glassmaking history is conventionally divided in three periods: the first from the 7th to 11th century, the second from the 12th to 15th century, the third up to now. The circulation of goods - but also of glassmakers and decorators - led to the establishment of a quite homogenous style in the Islamic world and today this often makes it difficult to attribute the various objects to one specific production centre.

In Persia and Mesopotamia in the first Islamic centuries, the production of carved glass and deep-cut glass or Sassanian derived relief, continued for all of the first period of Islamic glassmaking (7th-11th century). It is held that in Islamic Egypt too, the cutting technique was practised at least in the 10th and 12th century AD, thanks to the circulation of specialised artisans. The decorative repertoire of carved glass, both deep and relief, includes various geometric motifs, stylised plant motifs and animal figures, real or imaginary, and was applied to bottles, flasks, glasses and bowls.

A particular group of carved glass is that of double-layer cameo glass, with relief decorations carved onto the outside layer, which is generally coloured. This technique was adopted for two centuries starting from the middle of the 9th century AD in Mesopotamia and Iran.
A particular category of carved glass, unconnected to the Sassanian model, is that of coloured blown diamond point engraved with geometrical and figurative motifs, exported - very rarely - to China. They date back to the 9th century AD, perhaps even the 10th, and the production centres were situated in Syria and Mesopotamia.

Staining (German: Ätzung) was one of the most refined decorative techniques, used only on Islamic Egyptian and Syrian glass from the 8th to 12th century. It is generally called shine-painting, but incorrectly, because it rarely gave the glass that typical iridescence of ceramic glazing. It consists of decorations in a chromatic range from yellow to brown: red is obtained with silver oxide based paint, sometimes mixed with copper salts. From an artistic perspective, decoration using the staining technique reached its peak late, in the 11th and 12th centuries.

Polychromatic enamel and gold decoration techniques, which are technically different from staining, began at the end of the 12th century or the beginning of the 13th in Syria, probably in Raqqa, but their origins are unknown. The first objects made were small: glasses, bowls, small bottles, flasks. From the middle of the 13th century more varied and complex shapes were seen; candle holders, tray stands, cups with feet, handled vases, pilgrim flasks. From the 14th century blown decorated objects were produced of relatively large dimensions of various shapes: long-necked bottles and mosque lamps. In that century glassmakers and decorators were active mainly in Egypt. The most important period for chromatic and decoration variety was the middle of the 13th century while later works of large dimensions have more conventional decorations. Figurative decorations on glass for secular use include knights, musicians, courtesans, polo players, which were abandoned around the end of the 13th century, and animals which were always more stylised. Inscriptions were quite frequent. Christian figures and symbols are also present. The reasons for the sudden decline of this art are not entirely known. It is hypothesised that Tamerlane, who occupied Damascus at the beginning of the 15th century, took the best Syrian artisans to Samarkand.

A different model of Islamic glass making - which is equally as important - is the Roman tradition, which continued uninterrupted in the eastern provinces of the Roman Empire, in particular what is now Egypt, Israel, Lebanon and Syria. In these regions, hot decoration was developed, both with applications and mould-blowing. Containers for daily use were mainly produced, sometimes very basic and with no decoration. Hot working techniques essentially consisted of the application of threads, blobs or other details and mould-blowing spread in all the Islamic glassmaking areas, particularly in Iran, where hot working flourished from the 9th to 12th century. Something completely original was the relief decoration of inscriptions and decorative motifs which was hot-formed on the wall with the use of special callipers on the two ends, the intaglio motif at one end and relief at the other. This technique was often a cheaper substitute than intaglio, from which it took some decorative motifs.
Islamic glass, especially the one richly decorated with enamelling, found its way to Europe too, often brought back from the Holy Land during the Crusades and were held in the houses of noble families and ecclesiastical treasures. They were imported to both Arabic and Christian Spain, where imitations might have been produced, as a document from 1387 from Tortosa (Catalonia) attests.

Non-intaglio Islamic glass bear the pontil mark, unlike the majority of Roman glass objects which were evidently formed at the mouth with the use of a tool which is similar to the Venetian 'rocca', when possible.

An eastern model was proposed for very particular glass which were often vivaciously coloured found in Longobard sites in northern and central Italy. They are clearly different from contemporary objects from north-eastern Europe and were perhaps made by Italic glassworkers expressly for the Longobard invaders.

In the European market and the eastern one too, the void created by the decline of Islamic glasswork was filled by Venetian glassmaker products, which until the end of the 13th century stood out because of the quality of the glass and the production methods. The first Venetian document in which a glassworker's name is mentioned dates back to the year 982 AD. A certain Domenico 'fiolario' is named, that is, a bottle maker. While in the first centuries the glassmakers were active in Venice, over the course of the 13th century they spontaneously moved to Murano, an insular town near the city. That the Venetian glassworks had old roots in late Roman period glass production, is not to be excluded, given that in the Imperial Roman period important glass production flourished along the northern Adriatic. However, the Venetian glassmakers most definitely drew fundamental inspiration from Islamic and Byzantine glassworks in the development of an elite production. The import of scraps of glass from the East, of flux ash and, before this, the movement from the near East to Venice of natron around the same time, which is a natural sodium flux, to sodium plant ash over the course of the 12th century, some similar types and also the arrival in Venice of enamel painting - the pride of Islamic and Byzantine glassworks - are proof of the close dependency relationship between Medieval Venetian glassworks and that of the near East. As early as the 13th century, the glassworkers in Murano were organised into a corporation or Arte, whose first conserved statute or Capitulary was inaugurated in 1271.
The molten sodium glass in the Murano furnaces was of exceptional quality, decoloured using manganese dioxide or sometimes coloured especially for the details. The Venetian glass products were extremely varied: bottles, glasses, chalices, salt holders, cups, bowls, sauce and jam vases, chamber pots, lamps of various styles and decorations. The decorations consisted of the application of blobs of threads and relief motifs obtained by mould-blowing. Notable refinement of a production category are the glasses decorated with molten enamels of Islamic origin found in European and near eastern sites (the most famous is the glass signed by Magister Adrevandin, held at the British Museum) with European decorations consisting of coats of arms, heraldic animals, sacred figures. From 1281 to 1351, enamel decoration production was documented in Murano, due to the artisans who emigrated from Greece and Dalmatia, and the rare descriptions of decorated glass correspond to those held in museums. There is no confirmation - either in documents or iconographical - which allow us to attribute these works to workshops across the Alps, as has been suggested by some scholars.
In some Italian cities, some sporadic glassworks were active, and they mainly dealt with the production of habitual use glass. A real glass centre though was found in Altare, near Savona in Liguria, from at least the 13th century. Universities or glassworker corporations from 1495 on, trained the inhabitants of Altare, who were going to emigrate, in a profession which would allow them to live in a dignified manner. We know very little about their production style, which from the Renaissance probably imitated the style of Venetian glass which was very popular abroad too. Both in Italian medieval glass and that from northern Europe, we see the pontil mark.

In northern Europe too, the fall of the Roman Empire led to the decline of the art of glass production to the point that it took about a millennium to return to the glory of ancient times, which coincided with the glass Renaissance which spread from Venice. The most important heirs of the Roman glassworkers were the glassworkers of the Franco Empire in Northern France, in Renania and Belgium. The range of forms was quite limited and included glasses, bowls, yellowish or greenish glass bottles. A particular type was the claw beaker, characterised by abnormal appendices attached around the wall. Other widespread types were the cone-shaped or horn-shaped glasses. Other Franco types were found in south-eastern England, which were imported or produced locally. Anglo and Saxon glassworkers who probably came with the Germanic tribes which invaded England in the 5th century AD, founded glassworks in Kent. From the 7th to the 9th century, in progressively modified forms, coloured glass multiplied and attached decoration was the main one which spread: filaments of even contrasting colours, with the bottom and rods often of a twisted bicolour. From the middle of the 10th century to the 12th century, the political disturbances which made living and working in Europe difficult, led to a reduction and worsening quality of glass production.

In the 13th century and especially in the 14th century, there was a flourishing of glass art production even to the north of the Alps: France, Holland, Germany, especially in the Mosa and Reno valleys and Bohemia. Many 'forest glassworks' were active, which were small and spread, like the name suggests, in the thick forests where fuel and plants were available, like ferns and beech, while ash which is rich in potassium, was an excellent flux. Their objects were both dishes of green or yellow glass which was very impure, and thin blown objects which were almost uncoloured and were characterised by carefully shaped details.
The most frequent types were glasses decorated with attached glass prunted beakers (German: Nuppenbecher) and the glasses decorated with vertical ribbings obtained using moulds. Some regions developed particular types. In France a chalice with a high, thin stem with a ribbed or stretched large and low cup was very popular. In Argonne, chalices and glasses with delicate mould-blown relief decorations. In Bohemia, long glasses with attached blobs (Keulenglas).

Around the end of the 14th century and over the course of the 15th century, decorative refinement in medieval glass from across the Alps had disappeared, while the refined Venetian glass started to stand out.