American e-commerce retailer Overstock has doubled down on its cryptocurrency bet, adding Bitcoin Cash, Ethereum and Litecoin to Bitcoin as payments options for nearly four million products on its site.

Overstock has let customers buy goods with Bitcoin since 2014. Now it has teamed up with digital asset exchange ShapeShift to integrate other major cryptocurrencies, including Dash and Monero.

During checkout, customers will select their preferred cryptocurrency and submit the order before being prompted to transfer the coins, just as they would with any other digital wallet transaction. Overstock will then use ShapeShift to convert the cryptocurrencies to Bitcoin.

Patrick Byrne, CEO Overstock, says: "Overstock is pro-freedom, including the freedom of individuals to communicate information about value and scarcity without relying on a medium created through the fiat of unaccountable government mandarins. For that reason, we have been an early proponent and adopter of cryptocurrencies."

Byrne has been an enthusiastic Bitcoin and blockchain backer for several years, even setting up an Overstock DLT subsidiary, called Medici Ventures, to invest in startups and develop the technology.

In another pointer to the mainstreaming of virtual currencies, Fidelity Investments has started allowing clients to use its website to track their holdings of bitcoin, ethereum and litecoin alongside other traditional asset clases through an alliance with digital wallet provider Coinbase.