Contemporary research has highlighted the steady rise of individuals becoming radicalised via exposure to extremist discussion on the internet, with the ease of communication with other users that the internet provides playing a major role in the radicalisation process of these individuals. The aim of the present systematic review was to explore recent research into the utilisation of language in extremist cyberspaces and how it may influence the radicalisation process. The findings suggest that there are five prominent linguistical behaviours adopted by extremists online: Algorithmic, Conflict, Hate, Positive, and Recruitment. The results demonstrate that the main purpose of extremist language online is to shape the perceptions of users to see their associated group in positive regard, while simultaneously negatively framing outgroup opposition. This is then followed by encouraging conflict against the promoted ideologies’ perceived enemies. Limitations, future research, and implications are discussed in detail.