With the invention of the cryptocurrency Bitcoin in 2009, the world's first blockchain application was developed. While academic research gradually begins to investigate cryptocurrencies more closely and attempt to understand their functioning, technology is rapidly evolving and ecosystems grow exponentially. The research is still scattered and chaotic and has not produced common guidelines. Therefore, the question remains: how sustainable cryptocurrencies and their digital ecosystems are.Only a few models and frameworks take a holistic view on digital sustainability. Only two frameworks were identified that take distributed ledger technologies (blockchain) or cryptocurrencies into consideration: the three governance strategies for digital sustainability of Linkov et al. (2018) and 10 basic conditions of sustainable digital artifacts according to Stuermer, Abu-Tayeh and Myrach (2016). These two frameworks were combined into a new integrated sustainability framework for cryptocurrencies. The developed integrated sustainability framework consists of four dimensions and 12 categories.Existing secondary data, self-conducted social media interviews and practical insights gained through an ASIC mining experiment were used to fill the framework with sufficient data. It confirms Bitcoin's sustainability problems in energy consumption and scalability, highlights Ethereum's great potential as a blockchain platform and explains the higher scalability and faster payment of Ripple and IOTA.While 2017 marked the temporary peak of the cryptocurrency hype, 2018 was a transformative year in which the leading cryptocurrencies were increasingly occupying more specialised niches.

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