Circle Sets September 16 for Arc Public Mainnet

Circle said on August 5 that Arc, its blockchain project for payments and tokenized financial assets built on USDC, will open its public mainnet on September 16. The announcement sets a firm launch date and names 11 third-party founding validators, including Visa, Mastercard, BlackRock and DTCC.

Arc is currently a private mainnet with more than 100 institutional and ecosystem builders. Circle’s core USDC business reported $73.3 billion in circulation at the end of June and $14.8 trillion in onchain transaction volume during the second quarter. Those figures cover USDC activity across existing networks, not Arc, and they give the September launch something concrete to be measured against.

A private network until September 16

Circle describes Arc as a layer-one blockchain built for financial markets and real-time money movement. It is meant to handle payments, asset transfers and other financial activity directly on-chain using USDC.

The project has moved in stages since Circle first unveiled it on August 12, 2025, alongside its second-quarter earnings that year. A public testnet followed on October 28, 2025, drawing more than 100 companies. In May 2026, Circle raised $222 million in a presale of its native ARC token, valuing the network at $3 billion on a fully diluted basis, with participation from a16z, BlackRock, Apollo, ICE and Standard Chartered. The network has been in private mainnet since, ahead of the September 16 public launch.

The public mainnet will open Arc to a broader set of users and applications beyond the institutions and developers currently testing on the private network. USDC will be used to pay transaction fees.

>>> Read more: Visa Stablecoin Platform Opens in Limited Beta

Wall Street joins as validators

Circle named BlackRock, DTCC, Galaxy, Global Payments, ICE, Mastercard, MoneyGram, SBI Group, Standard Chartered, Sumitomo Corporation and Visa as founding third-party validators, alongside Circle itself.

Validators confirm transactions and maintain a blockchain’s shared record and Arc uses a permissioned set. Unlike networks where anyone meeting technical and financial requirements can join, Circle controls who holds that role.

Circle describes Arc’s application layer as open and permissionless. Anyone can build and deploy applications on the network without prior approval. Whether that holds under real traffic is worth watching once the network is processing transactions from outside users.

Naming a validator is not the same as launching a product on Arc. Circle expects these institutions to help secure the network; it says nothing about whether any of them has moved assets onto it yet.

Not every integration has a date

BlackRock is expected to deploy BUIDL, its tokenized Treasury fund, on Arc, though Circle gave no deployment date.

DTCC’s work with Circle covers infrastructure for tokenizing assets held through the Depository Trust Company. That connection is not scheduled to begin until the second half of 2027, well past the September launch.

Circle also named a group of payment providers, exchanges, wallets and decentralized finance platforms it expects to support Arc, including Kraken, Ledger, MetaMask, Wirex and Uniswap. Being on that list is not the same as being live on day one.

>>> Read more: Visa Launches USDC Settlement for U.S. Banks

Circle’s other network scaled slowly, then fast

Circle has run this playbook once already. The Circle Payments Network, its existing system for institutional money movement, launched in May 2025. By the end of the second quarter of 2026, more than a year later, it had reached $14.7 billion in annualized transaction volume for the trailing 30 days, with 175 financial institutions enrolled. As recently as March 2026, that annualized figure stood at $8.3 billion. The jump to $14.7 billion happened within a single quarter.

Arc’s founding validators, a comparable roster of banks, card networks and market infrastructure firms, face the same distance between naming a partnership and running production volume through it. CPN took roughly a year to move past modest activity before volume accelerated.

CPN’s trajectory gives Arc a working comparison once the public mainnet opens: whether the validators and integrations named this week show up in transaction data on a similar timeline, or faster, given Arc launches with more institutional backing already in place than CPN had at its start.