German linguists consider any version of speech that is traceable to a specific German tribe to be a “dialect” (as in Saxon or Franconian or Allemannic). Any version of Hochdeutsch that is distinguished by its rhythm, pronunciation or a few non-standard words, is considered to be a regional accent of Standard German, and not a dialect.
The principal dialects of German divide into “Low German,” (often called “Low Saxon”) and dialects of “Upper German,” (including “Upper Saxon”). Localized dialects still exist in profusion, and a good many of them are not intelligible to a speaker of Hochdeutsch.
Low German is more general term for the Low Saxon versions of German spoken in the far north of the country and towards the west (modern Netherlands). Like “Low Franconian,” a neighboring dialect, Low Saxon did not partake in the “High German Consonant Shift.” As a living, spoken language, Low Saxon is in decline. At one time, during the “Middle German” period, Low German was the lingua franca of the Hanseatic League, and was spoken from Norway to Russia. It was the language of Prussia. The widespread acceptance of Protestantism and the Luther Bible in the 16th century caused Early New High German to become much more influential, and the importance of the Hanseatic League itself declined as new trade routes to Asia and the New World were discovered. Soon, Low Saxon was no longer taught in the schools. It was spoken only by the uneducated and generally only in the home.
Moselle-Franconian is a version of Hochdeutsch that has become the standard for Luxembourg. Other Central German dialects of Hochdeutsch include Hessian, Upper Saxon, and other versions of Franconian. Some inhabitants in southeastern Belgium and the Netherlands still speak Hochdeutsch.
“Upper German” divides into Alemannic (Swiss German), Swabian, Alsatian, and Austro-Bavarian. East Franconian is another area of Upper German. Liechtenstein and Austria both commonly speak Upper German dialects. Poland and Romania also have areas in which Upper German dialects are still spoken.