In many parts of the world, wide-ranging atrocities and other human rights abuses continue to threaten populations, especially those belonging to minority groups and indigenous peoples. As the reach of social media grows ever more pervasive globally, so too does its impact in contexts where genocide, mass killing, or systematic violent repression have occurred or there is a risk of such things taking place. The country situations at the top of the 2019 Peoples under Threat index illustrate how, in case after case, social media is playing a major role in encouraging the killing. Social media platforms now occupy a central role in stigmatizing target groups, legitimizing violence and recruiting the killers. Deliberate misinformation, including false allegations and dehumanization of targeted groups, has been an enduring feature of conflict over the ages. But in the social media age, the process has accelerated to an unprecedented degree. Ease of access to social media has given every violent racist a potential public platform, and the anonymity of social media has given states the ability to incubate and incite hatred across international borders. Conflict narratives, conspiracy theories and extremist views quickly find a home on platforms where every voice competes for attention, and the moderate voices and restrained language necessary for peace-building are drowned out. Political leaders, rebel groups, activists and ordinary civilians have all used social media as a tool for communication. Even in the most fragile and divided societies where internet access remains minimal, such as South Sudan, the role of social media is growing, as traditional media landscapes and technologies rapidly transform. Syria’s devastating conflict, on the other hand – where social media platforms are used by all sides and videos uploaded to YouTube have received hundreds of millions of views – has led to it being repeatedly described as a ‘social media war’. Social media promises to increasingly influence how conflict and episodes of violence are perceived, their trajectories, and the ways they are responded to. No divided society or context of conflict can be understood without considering how social media is being used by an array of state and non-state actors. Indeed, critics have accused social media firms of accepting too little responsibility for the use of their technologies to foment division and violence in unstable and conflict-affected societies. Many point to Myanmar – where the United Nations (UN) has called for authorities to face charges of genocide – as 2 the starkest example of the link between social media and the commission of atrocities. There dehumanizing language and outright incitement to mass murder were amplified via Facebook and Twitter, contributing to the widespread targeting of the mainly Muslim Rohingya minority. In November, Facebook released a report it had commissioned related to the killing of Rohingya which concluded that ‘Facebook has become a means for those seeking to spread hate and cause harm’. But while the company acknowledged that ‘we can and should do more’, Facebook and other social media corporations continue to rely on self-regulation, based heavily on moderation in line with ‘community standards’ - an approach which has proved woefully ineffective when confronted by organized, and at times officiallysanctioned, campaigns of violent hatred. Peoples under Threat draws much-needed attention to numerous other cases where, in the context of social cleavages, political instability and insecurity, social media risks exacerbating or paving the path to systematic violent repression or mass killings. In many of those countries where the risk of mass atrocity crimes is most pronounced, the internet-savvy youth often outnumbers the rest of the population. Where deadly armed conflict rages on, from Libya to Afghanistan, combatants often wield a gun in one hand and a smartphone in the other – their cameras weaponized in a propaganda war uniting battlefields and cyberspace. Social media is a tool in the hands of states brutally oppressing their populations, as in Syria, where supporters of President Bashar al-Assad popularized a #SyriaHoax hashtag on Twitter to discredit evidence of horrific chemical attacks on civilian targets, such as in Khan Sheikhoun and Douma. Social media can also be manipulated by outside powers to generate support for policies that harm civilians. Saudi Arabia and the United Arab Emirates (UAE), for example, have used ‘bot armies’ to legitimate their bombing campaign in Yemen, while rising hostilities between India and Pakistan following the killing of 40 Indian soldiers in Kashmir were stoked by the trending of rival Twitter hashtags by nationalists in the two countries. In conflict zones such as Afghanistan and Cameroon, where threats are on the rise, armed groups ranging from the Taliban to Anglophone separatists rely on social media platforms for a range of activities: to coordinate movements, recruit supporters and fighters, glorify victories and dispute opposing narratives, and solicit funds. The so-called Peoples under Threat 2019