The first functioning implementation of a proof-of-stake cryptocurrency was Peercoin, introduced in 2012.[1] Other cryptocurrencies, such as Blackcoin, Nxt, Cardano, and Algorand followed.[1] However, as of 2017[update], PoS cryptocurrencies were still not as widely used as proof-of-work cryptocurrencies.[5] The biggest proof-of-stake blockchains by market capitalization in 2021 were Cardano, Avalanche, Polkadot and Solana. Other prominent PoS platforms include Tron, EOS, Algorand, and Tezos.[6][7][8][9]