Chapter 7 focuses on social media dynamics in the mobilisation of support for, or opposition to, refugees. An analysis of online commenting by news readers sheds light on the more hidden side of the public sphere, where people may seize the chance to express emotions and translate them into political action. This is particularly interesting because the case of solidarity with refugees has divided public opinion all over Europe with advocates of human rights and open borders opposing supporters of exclusive, nationalist welfare. The chapter analyses how bottom-up contestation of refugee solidarity was triggered by particular events and their interpretation in the media, such as the humanitarian disasters at Europe’s external borders that unfolded during the month of September 2015. In particular, a comparative analysis of online commenting on Facebook news sites is undertaken for eight countries (Denmark, France, Germany, Greece, Italy, Poland, Switzerland and the UK) in order to assess the political expressions of selected citizen-users who decide to position themselves in debates about refugees. Social media offers an interesting opportunity for citizens to ‘take voice’ or ‘take sides’, which is the precondition for any form of political mobilisation. At the reception site, opinions in the form of general attitudes expressed towards refugees as shaped by media discourse can be measured, as can responsiveness, either in the form of consenting or opposing claims raised in the media. Voices in the form of political statements made by those citizen-users who intervened in the debate as ‘secondary definers’ of the events are also assessed.