What is cirBTC?

Circle Wrapped Bitcoin (cirBTC) is a 1:1 BTC-backed token issued by Circle on Ethereum with real-time onchain reserve verification through Chainlink Proof of Reserves.

cirBTC is Circle Wrapped Bitcoin—a tokenized representation of Bitcoin (BTC) issued by Circle on Ethereum. Every cirBTC is backed 1:1 by native BTC held at a regulated entity in the Circle group of companies. The BTC is held for the exclusive benefit of cirBTC holders and segregated from Circle’s corporate assets.

Why cirBTC?

Bitcoin is the most widely held digital asset, yet it cannot natively interact with smart contracts, limiting its use in lending, borrowing, or complex trading strategies. cirBTC solves this by creating a tokenized version of BTC that operates on smart contract blockchains, transforming idle Bitcoin into productive capital.

• 1:1 backed by native BTC: every cirBTC is redeemable for the underlying Bitcoin.
• Real-time proof of reserves: onchain verification through Chainlink rather than periodic attestations.
• Neutral issuer: Circle does not operate a competing exchange or lending protocol.

Paired with USDC, cirBTC enables institutional workflows such as posting cirBTC as collateral to borrow USDC and access capital without selling the underlying Bitcoin position.

Access and availability

cirBTC is available to qualified businesses through Circle Mint. Contact Circle to learn more.

Mint and redeem cirBTC using the same API endpoints as USDC and EURC, with CIRBTC as the currency code. For step-by-step instructions, see the Mint and redeem cirBTC quickstart.

cirBTC is available on the following blockchains:

• Ethereum: mainnet and Sepolia testnet
• Arc: testnet

Developers can test cirBTC integrations using the Circle faucet to obtain testnet cirBTC, and the sandbox environment to test API interactions.

cirBTC in the API

cirBTC uses the currency code CIRBTC in all Circle Mint API calls. You interact with it the same way you use USD (for USDC) or EUR (for EURC) when creating transfers, deposit addresses, and other operations.

For example, to create a deposit address for cirBTC on Ethereum:

curl -X POST https://api.circle.com/v1/businessAccount/wallets/addresses/deposit \
  -H "Authorization: Bearer ${YOUR_API_KEY}" \
  -H "Content-Type: application/json" \
  -d '{"idempotencyKey":"unique-uuid","currency":"CIRBTC","chain":"ETH"}'

For supported blockchains and blockchain codes, see Supported chains and currencies. To get started with your first mint or redemption, see the Mint and redeem cirBTC quickstart.