> ## Documentation Index
> Fetch the complete documentation index at: https://developers.circle.com/llms.txt
> Use this file to discover all available pages before exploring further.

# 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

<Note>
  cirBTC is available to qualified businesses through [Circle Mint](/circle-mint).
  [Contact Circle](https://www.circle.com/mint-contact) to learn more.
</Note>

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](/circle-mint/quickstarts/mint-and-redeem-cirbtc).

cirBTC is available on the following blockchains:

* **Ethereum**: mainnet and Sepolia testnet
* **Arc**: testnet

Developers can test cirBTC integrations using the
[Circle faucet](https://faucet.circle.com/) to obtain testnet cirBTC, and the
[sandbox environment](https://app-smokebox.circle.com) 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:

```bash theme={null}
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](/circle-mint/references/supported-chains-and-currencies).
To get started with your first mint or redemption, see the
[Mint and redeem cirBTC quickstart](/circle-mint/quickstarts/mint-and-redeem-cirbtc).