<p>Calls to amplify marginalized voices are common. In this paper, we examine these calls by paying close attention to how the structure of online environments shape practices of amplification, and what this means for political communication and digital activism. We develop a conceptual and normative framework for understanding amplification as a technologically mediated practice of digital activism by answering three questions. Firstly, what is amplification, in the sense that features in calls to amplify marginalized voices? Second, what is at stake in amplifying well or badly? Third, how should those to whom calls to amplify are addressed respond? In answering the first question, we develop an account of amplification by exploiting an analogy with the amplification of sound in acoustics. In answering the second question, we identify several benefits of amplifying well and costs of amplifying badly. In answering the third question, we identify several heuristics that can be employed to increase the chances of achieving the benefits of successful amplification and reduce the chances of unsuccessful amplification.</p>