These were used for non-scriptural texts, letters, accounting records, notes, and all the other types of written documents.

Letters following a large initial at the start of a paragraph or section often gradually diminish in size as they are written across a line or a page, until the normal size is reached, which is called a "diminuendo" effect, and is a distinctive Insular innovation, which later influenced Continental illumination style.

Within this system, the palaeographer Julian Brown identified five grades, with decreasing formality: Brown has also postulated two phases of development for this script, Phase II being mainly influenced by Roman uncial examples, developed at Wearmouth-Jarrow and typified by the Lindisfarne Gospels.

[citation needed] The Tironian et, ⟨⁊⟩ – equivalent of ampersand ⟨&⟩ – was in widespread use in the script (meaning agus 'and' in Irish, and ond 'and' in Old English) and is occasionally continued in modern Gaelic typefaces derived from Insular script.

Unicode treats representation of letters of the Latin alphabet written in insular script as a typeface choice that needs no separate coding.

According to Michael Everson, in the 2006 Unicode proposal for these characters:[6] To write text in an ordinary Gaelic font, only ASCII letters should be used, the font making all the relevant substitutions; the insular letters [proposed here] are for use only by specialists who require them for particular purposes.