The reduction happened at the same time as phonetic changes that led to a greater number of different phonemes in the spoken language, when Proto-Norse evolved into Old Norse.

Usage of the Younger Futhark is found in Scandinavia and Viking Age settlements abroad, probably in use from the 9th century onward.

[citation needed] Literacy in the Younger Futhark became widespread in Scandinavia, as witnessed by the great number of Runestones (some 3,000), sometimes inscribed with almost casual notes.

In tabular form: The Younger Futhark became known in Europe as the "alphabet of the Norsemen", and was studied in the interest of trade and diplomatic contacts, referred to as Abecedarium Nordmannicum in Frankish Fulda (possibly by Walahfrid Strabo) and ogam lochlannach "Ogham of the Scandinavians" in the Book of Ballymote.

In the Middle Ages, the Younger Futhark in Scandinavia was expanded, so that it once more contained one sign for each phoneme of the old Norse language.

Inscriptions in medieval Scandinavian runes show a large number of variant rune-forms, and some letters, such as s, c and z, were often used interchangeably.

[3] According to Carl-Gustav Werner, "in the isolated province of Dalarna in Sweden a mix of runes and Latin letters developed".

Some discussion remains on whether their use was an unbroken tradition throughout this period or whether people in the 19th and 20th centuries learned runes from books written on the subject.