Circle Launches Wrapped Bitcoin (cirBTC) With Chainlink Proof of Reserve

Circle has launched Circle Wrapped Bitcoin (cirBTC), a 1:1 $BTC-backed token that brings native Bitcoin onto programmable networks with segregated custody and verifiable onchain reserve data. Announced on 4 September 2026, cirBTC is now live on Ethereum, with native support planned for Circle's Arc layer-1 blockchain once its mainnet launches.

How cirBTC's Backing Is Structured

Every cirBTC token is backed one-to-one by native Bitcoin and redeemable one-to-one for it, making it a wrapped token rather than a staked or derivative product. The underlying $BTC is held through a Circle affiliate and custodied by Circle National Trust, a federally chartered national trust bank supervised by the Office of the Comptroller of the Currency. That national trust charter places the custody arrangement under US federal banking oversight, a structure designed to give regulated institutions a clearer path to hold the underlying asset. Reserves are held in accounts segregated from Circle's corporate assets and maintained for the exclusive benefit of cirBTC holders, keeping the collateral legally and operationally separate from the issuer's balance sheet. The token is issued by Circle International Bermuda Limited, a Class F Digital Asset Business licensed by the Bermuda Monetary Authority.

Chainlink Proof of Reserve for Verifiable Backing

Circle pairs segregated custody with observable backing by connecting three data points: the native $BTC held in disclosed reserve addresses, the onchain reserve value published through Chainlink Proof of Reserve, and the circulating cirBTC supply across supported chains. Chainlink Proof of Reserve is already used across the industry to let smart contracts verify reserve data onchain, and adopting it here brings a familiar verification pattern to a new wrapped-BTC product. When cirBTC is redeemed, the corresponding tokens are removed from circulation and native $BTC is released, so the number of tokens in circulation should not exceed the $BTC held in reserve. Circle notes that proof of reserve does not replace custody, redemption, or smart-contract diligence, but it allows lending protocols, market makers, and asset managers to inspect the collateral without relying solely on the issuer's statement.

Ethereum Now, Arc and More Later

cirBTC enters an already competitive wrapped-Bitcoin market in which custody and reserve transparency have become the key differentiators for institutions deciding how to deploy $BTC in decentralized finance. Wrapped Bitcoin (WBTC) has long been the dominant Ethereum-based form of tokenized BTC, and newer entrants have competed by emphasizing alternative custody and attestation models, which is the same axis on which cirBTC is positioning itself. The launch also extends Circle's reach beyond its $USDC stablecoin franchise, following moves such as bringing $USDC to Hyperliquid. Native cirBTC support on Arc is expected at mainnet launch, subject to applicable regulatory approvals, with additional blockchain integrations planned over time. For holders, the proposition is straightforward: a way to use Bitcoin in onchain markets — as seen when WBTC exchange outflows recently hit a six-week high — while keeping the reserve side of that exposure observable. What to watch next is whether DeFi protocols integrate cirBTC as collateral and whether the disclosed reserve addresses and Chainlink feeds are consistently maintained as supply grows.