The app that runs South Korea's money is testing a won stablecoin

South Korea's dominant fintech platform eyes on-chain settlement

Toss (@toss__official), the financial super-app operated by Viva Republica, has signed a memorandum of understanding with @Optimism and privacy technology firm Sunnyside Labs to explore a Korean won-backed stablecoin built on the OP Stack. The collaboration will begin with a three-month proof of concept evaluating whether the OP Stack can support the compliance, privacy, and performance requirements needed for regulated financial institutions.

Launched in 2015, Toss has grown into South Korea's largest fintech platform, offering payments, banking, investments, credit scoring, ID verification, tax, and insurance. The super-app surpassed 30 million users as of July 2025, representing nearly 60% of South Korea's total population. The scale of that user base makes the pilot notable: a successful launch would place a won-denominated stablecoin in front of one of the largest consumer fintech audiences in Asia.

The proof of concept will focus on three key validation points: whether financial institutions can directly control payment and settlement processes, whether KYC and AML requirements can be technically implemented, and whether individual transaction information can be securely protected on a public network.

Privacy, compliance, and the road to a real product

The companies will evaluate payment settlement, compliance requirements, and privacy protection using Optimism's OP Stack and Sunnyside Labs' Privacy Boost technology. Privacy Boost is designed to address a key limitation of public blockchains, where transaction details are generally visible to all participants. The technology allows sensitive financial data to remain private while still enabling regulated institutions to verify transactions and maintain compliance standards.

The work fits into Toss's "Money 3.0" strategy, which aims to build payment and remittance rails on top of stablecoins instead of relying only on bank transfers. The firm has already registered 24 trademarks for KRW stablecoins, including names such as "TOSSKRW," and is developing a Web3 wallet inside its super-app to deliver on-chain services to regular users.

The pilot is not a product launch. Three months is a short window for a proof of concept, and the gap between technically feasible and regulatorily approved can be measured in years in South Korea. No regulatory approvals have been granted, and no specific token issuance details have been disclosed. The initiative follows similar moves from other South Korean financial institutions, including Shinhan Card, which teamed with the Solana Foundation in late April to test the commercial feasibility of stablecoin payments.

Over the past year, the OP Stack has also been selected by Bitpanda for its MiCA-compliant blockchain in Europe, adopted by Kraken through its Ink network, and used by Mitsui and Co. Digital Commodities in Japan for tokenized precious metals, signalling growing institutional appetite for the infrastructure beyond the decentralized finance sector.

Sources
crypto.news: South Korean super-app Toss partners with Optimism for won-linked stablecoin trial
The Asia Business Daily: Toss Partners with Optimism and Sunnyside Labs to Validate Won-Based Digital Financial Infrastructure
The Korea Herald: 6 in 10 South Koreans use Toss app