Historically, issues relating to environmental sustainability have featured little in digital ethics debates, with scholars predominantly focusing on challenges associated with, for example, consent, privacy, power, fairness and discrimination. In this chapter, we focus on the growing trend to include environmental sustainability as an issue in the academic discussion on the ethics of digital technologies. We explain this trend, which includes considerations of how to mitigate the environmental harms associated with digital technology design, development and implementation. We describe how scholars have approached these issues, and what questions remain to be addressed around the sustainability of digital technologies in future ethics research. In particular, we describe how mainstream discourse often positions digital technologies as helping to address environmental sustainability concerns, and we provide a number of examples to where this has been the case. We then draw on the literature from social sciences and humanities, and particularly the concept of technological solutionism, to show how this framing can hide (environmental) sustainability harms caused and/or amplified by these innovations, and we illustrate these harms in detail. We then analyse recent debates advanced in the digital ethics scholarship that is attempting to engage with these harms, and in particular, how these harms can be encapsulated in our moral thinking about digital technologies. We show how, while progress is being made at fast pace, this body of literature remains underdeveloped, with many normative questions remaining. We describe two of these specific questions that need further discussion - questions around weighing up values in practice, and responsibility - and call for these to be part of any future research agenda.