The ASCL has a three-level hierarchical structure. The most detailed level of the classification consists of languages which are represented by four-digit codes. The second level of the classification comprises narrow groups of languages (the Narrow group level), identified by two-digit and three-digit codes. The most general level of the classification consists of broad groups of languages (the Broad group level) and is identified by one-digit codes. The classification includes Australian Indigenous languages and sign languages.

For example, the Lithuanian language has a code of 3102. In this case 3 denotes that it is an Eastern European language, while 31 denotes that it is a Baltic language. The Pintupi Aboriginal language is coded as 8713. In this case 8 denotes that it is an Australian Indigenous language and 87 denotes that the language is a Western Desert language.

Language data may be output at the Broad group level, Narrow group level or the language level of the classification. Also, significant languages within a Narrow group can be presented separately with the remaining languages of the Narrow group aggregated. The same principle can be adopted to highlight significant Narrow groups within a Broad group.

Australian Institute of Health and Welfare

The first edition of the ASCL was published in 1997. The ASCL was revised in 2005, 2011 and 2016.