Abstract
This editorial article introduces the OSNEM special issue on Detecting, Understanding and Countering Online Harms. Whilst online social networks and media have revolutionised society, leading to unprecedented connectivity across the globe, they have also enabled the spread of hazardous and dangerous behaviours. Such 'online harms' are now a pressing concern for policymakers, regulators and big tech companies. Building deep knowledge about the scope, nature, prevalence, origins and dynamics of online harms is crucial for ensuring we can clean up online spaces. This, in turn, requires innovation and advances in methods, data, theory and research design - and developing multi-domain and multi-disciplinary approaches. In particular, there is a real need for methodological research that develops high- quality methods for detecting online harms in a robust, fair and explainable way. With this motivation in mind, the present special issue attracted 20 submissions, of which 8 were ultimately accepted for publication in the journal. These submissions predominantly revolve around online misinformation and abusive language, with an even distribution between the two topics. In what follows, we introduce and briefly discuss the contributions of these accepted submissions.