This is the approximate extent of Old Norse and related languages in the early 10th century.
The Old EastNorse dialect was spoken in Denmark and Sweden and settlements in Russia, England and Normandy.
Its modern descendants are the West Norse languages of Icelandic, Norwegian (nynorsk), Faroese and the extinct Norn language of the Orkney and the Shetland Islands as well as the East Scandinavian languages of Swedish, Danish and Norwegian (bokmål/riksmål).
Old EastNorse is in Sweden called Runic Swedish and in Denmark Runic Danish, but until the 12th century, the dialect was the same in the two countries.
A change that separated Old EastNorse (Runic Swedish/Danish) from Old West Norse was the change of the diphthong æi (Old West Norse ei) to the monophthong e, as in stæin to sten.
From 1100 and onwards, the dialect of Denmark began to diverge from that of Sweden.