Contesting hate focuses on digital attempts to contest Islamophobic narratives during a historical period where racialised Islamophobia has shifted beyond the domain of the extreme right and been legitimised in a range of national contexts. The capacity of social media to contest hate speech is heavily debated. However, in increasingly polarised democracies, it is important to ask which conditions enable counter-narratives against hate to emerge, as well as to identify the conditions that undermine them. To answer these questions, the book draws on a unique five-year dataset, which includes a corpus of almost 4 million tweets related to three 'trigger events': the Christchurch terrorist attacks, Brexit and the Covid-19 pandemic, alongside interviews with digital activists. The analysis reveals the contrasting ways Islamophobia is articulated and mobilised in the context of white supremacism, Hindu nationalism and 'culture wars' debates. It identifies the limits and potentials in varied attempts to contest Islamophobia: ranging from hashtag and counter-narrative campaigns led by NGOs, to (sometimes counter-productive) attempts by would-be allies to call out racism and political hypocrisy. It demonstrates the specific event-user-platform dynamics that enable or limit the circulation of online hate speech, and the ambivalences associated with attempts to contest it in a context where the moderation of Twitter was stricter and users who propagated hate were removed. In the process, the book develops an interdisciplinary approach across media studies, computer science, sociology and cultural theory, to set out a new theoretical and methodological framework for understanding digital hate and mediated activism.