RESEARCH CONTEXT An estimated 25,000 foreign fighters have been recruited to Islamic State (IS) from over 100 counties around the world. While shocking in itself, this reflects only the militant end-product of the radicalisation process. Before militancy emerges, IS supporters use mainstream social media in English to socialise, radicalise and recruit foreigners. For example, the fourth IS 'Clanging of the Swords' film racked up millions of views on video-sharing platforms, and created vast excitement among those who followed ISIS online. This use of online communications in English by supporters of Islamic State (IS) presents two unprecedented research opportunities: first, to predict the spread of extremism in English-speaking populations; and second, to understand how online communications shape people's understanding of IS and its opponents. However, currently there is no method to analyse longitudinal social media data to investigate the processes underlying the radicalisation of social media users. The proposed research provides a timely opportunity to refine methods, software and analytics to maximise the impact that psychology and computer science can make to countering extremism. The central research questions are how and why people develop allegiance to extremist groups through communicating online. To do this, we will develop the functionalities and capabilities of an existing software suite that can harvest and analyse large volumes of publicly-available Twitter data ('Tweets'). AIMS AND OBJECTIVES The central aim of this project is to develop conceptually-grounded social media analytics software to investigate the socialisation and radicalisation of mainstream users. As a by-product of this process, and secondary aim, we will establish how supporters of radical Islam use online communications in English to affect how their target audience defines both themselves and their opponents in relation to IS. APPLICATIONS AND BENEFITS This project will deliver a software tool that can analyse longitudinal big data. This software will be open source and freely available. This means that it will have the potential to make a big impact in social science. It will be applicable to, and usable by, any researcher or practitioner interested in analysing social media data. PROJECT TEAM Our project brings together a multi-disciplinary team of academics and will be steered by end-users, mediated by Defence Science and Technology Laboratory, whose expertise will enable us to maximise the usefulness and applicability of the software tools. On the academic side, we have assembled a team with interdisciplinary strengths in computer science, psychology and social media data analysis to understand the needs of social scientists and successfully develop technology that will become fully embedded in social science and social media research.