The early Anglo-Frisian varieties, like Old English and Old Frisian, and the third Ingvaeonic group at the time, the ancestor of Low German Old Saxon, were spoken by intercommunicating populations.

While this has been cited as a reason for a few traits exclusively shared by Old Saxon and either Old English or Old Frisian,[1] a genetic unity of the Anglo-Frisian languages beyond that of an Ingvaeonic subfamily cannot be considered a majority opinion.

[1][2] Geography isolated the settlers of Great Britain from Continental Europe, except from contact with communities capable of open water navigation.

West Frisian, by far the most spoken of the three main branches with 875,840 total speakers,[11][full citation needed] constitutes an official language in the Dutch province of Friesland.

[1] These are the words for the numbers one to 12 in the Anglo-Frisian languages, with Dutch, West-Flemish and German included for comparison: * Ae [eː], [jeː] is an adjectival form used before nouns.

[f] The extinction of two little-attested and presumably North Sea Germanic languages, Old Old Anglian and Old Jutish, in their homelands (modern southern Schleswig and Jutland respectively), may have led to a form of "survivorship bias" in classification.