MetaMask, the popular cryptocurrency wallet for the Ethereum blockchain, is testing an entirely on-chain payment card running on Mastercard's giant network and issued by Baanx, according to promotional materials and a testing platform seen by CoinDesk.

Such a product would unite two giants of their respective fields. MetaMask is the biggest self-custody wallet with more than 30 million monthly active users, while Mastercard provides key plumbing in the conventional financial system through its credit- and debit-card network spanning the globe.

The MetaMask/Mastercard payment card would be "the first ever truly decentralized web3 payment solution," allowing users to spend their crypto "on everyday purchases, everywhere cards are accepted," according to the marketing materials.

Mastercard and its rival Visa have been quietly courting public blockchain developer communities and self-custody wallet providers of late. Mastercard has been working with hardware wallet firm Ledger as well as MetaMask, CoinDesk reported in October of last year.

Visa, meanwhile, has been working with the USDC stablecoin and the Solana blockchain on cross-border payments and smoothing out wrinkles like paying Ethereum gas fees.

MetaMask developer Consensys did not respond to a request for a comment.

When contacted by CoinDesk, a Mastercard representative pointed to the firm's statement from October: "Mastercard is bringing its trusted and transparent approach to the digital assets space through a range of innovative products and solutions – including the Mastercard Multi-Token Network, Crypto Credential, CBDC Partner Program, and new card programs that connect Web2 and Web3."

UPDATE (March 11, 2024, 21:33 UTC): Adds that Baanx will issue the card.