[12] Central- and southwestern Jämtland dialects have preserved the Old Norse primary diphthongs ai, au, ey, usually with pronunciations like [e̞i̯], [ɞɵ̯], [œy̯].

[13] In the Offerdal parish in western Jämtland, ai and ey have monophthongized to [ɛː] and [œː],[14] while au is preserved as [æɵ̯].

[13] Eastern Jämtland dialects (spoken in the parishes Borgvattnet, Ragunda, Fors, Stugun, Håsjö, Hällesjö) have no diphthongs, but have monophthongized ai to [e̝ː], ey to [ø̝ː], and au to [ɵː], [ɞː], [ʌː] or [o̞ː].

The most prominent application of this orthography has been to prepare translations of parts of the Bible into the dialect, resulting in the book Nagur Bibelteksta på jamska.

Another spelling convention in Nagur Bibelteksta på jamska is the use of the digraph "sh", in e.g. "mänish" n. 'human being' and "fishn" n. 'the fish', with the same pronunciation as English 'sh' in 'shoe'.

People writing Jämtland dialects commonly use the letters of the Swedish alphabet, with the addition of æ and ô.