The classification and sub-classification of Digo provides a good example of the difficulty sometimes faced by linguists in differentiating languages and dialects. Most contemporary authorities follow Nurse and Hinnebusch (1993) in classifying Digo as a dialect of Mijikenda, one of the constituent languages of the Sabaki group of Northeast Coast Bantu. The Mijikenda dialects are indeed mutually intelligible, though they are conventionally treated as separate languages. Digo is a member of the southern Mijikenda sub-group, and is most closely related to its neighbours Duruma and Rabai. It is, however, felt by speakers to be sufficiently different from other Mijikenda dialects to deserve its own orthography and literature.

Digo speakers recognise in turn a number of named varieties or dialects of their language. These are:

• Chinondo (Northern Digo), spoken along the south Kenya coast between Likoni (south Mombasa) and Msambweni (Hinnebusch 1973);
• Ungu (or Lungu, Southern Digo), spoken on the coastal strip south of Msambweni and across the border into northern Tanzania (Hinnebusch 1973);
• Ts’imba, spoken in the Shimba Hills of Kenya between Vuga in the east and Ng’onzini in the west (Walsh 2006); and
• Tsw’aka (or Chw’aka), spoken in and around the village of the same name on the Shimoni Peninsula of Kenya (Möhlig 1992, Nurse & Walsh 1992).

Tsw’aka was once thought to have been a local variety of the Vumba dialect of Swahili, but is now considered to be a variety of Digo in the process of shifting to Vumba. Some assimilated Segeju and Degere are also said to speak their own separate varieties of Digo, presumably as a consequence of language shift (Nurse & Walsh 1992).

Digo speakers usually write their language using an alphabet based on the Latin alphabet used for Swahili, with additional combinations of letters representing some of the sounds that are distinctive to Digo (e.g. 'ph' for the voiced bilabial fricative or approximant). This has been developed further by the Digo Language and Literacy Project of Bible Translation and Literacy (East Africa). The project has produced basic literacy materials^[1] and published a Digo-English-Swahili Dictionary using the new orthography (Mwalonya et al. 2004) as well as a linguistic description in A Grammar of Digo (Nicolle 2013). The Digo New Testament was finished in 2007. All of these materials are based on the Northern Digo dialect spoken in Kenya.

One hundred Digo proverbs have been collected and published by Margaret Wambere Ireri, with translations into Swahili, English, and French.^[3]

• Hinnebusch, T.J. (1973). Prefixes, Sound Change, and Sub grouping in the Coastal Kenyan Bantu Languages (PhD dissertation). UCLA.
• Möhlig, W.J.G. (1992). "Language Death and the Origin of Strata: Two Case Studies of Swahili Dialects". In Brenzinger, M. (ed.). Language Death: Factual and Theoretical Explanations with Special Reference to East Africa. Mouton de Gruyter. pp. 157–179.
• Mwalonya, J.; Nicolle, A.; Nicolle, S.; Zimbu, J. (2004). Mgombato: Digo-English-Swahili Dictionary. Nairobi: BTL.
• Nicolle, Steve (2013). A Grammar of Digo: A Bantu language of Kenya and Tanzania. Dallas, TX: SIL International.
• Nurse, D.; Hinnebusch, T.J. (1993). Swahili and Sabaki: A Linguistic History. University of California Publications in Linguistics. Vol. 121. University of California Press. ISBN 9780520097759.
• Nurse, D.; Walsh, M.T. (1992). "Chifundi and Vumba: Partial Shift, No Death". In Brenzinger, M. (ed.). Language Death: Factual and Theoretical Explanations with Special Reference to East Africa. Mouton de Gruyter. pp. 181–121.
• Walsh, Martin T. (2006). "A Click in Digo and its Historical Interpretation". Azania. 41 (41): 158–166. doi:10.1080/00672700609480440. S2CID 161227106.

• Digo dictionary, grammar and publications