Circle launches cirBTC testnet on Arc, Ethereum

Circle has started the public test phase for cirBTC, its planned wrapped-Bitcoin product, by making testnet support available on Arc Testnet and Ethereum Sepolia. The company’s public faucet now includes cirBTC alongside testnet USDC and EURC, and Circle’s developer materials show Arc Testnet and Ethereum Sepolia as supported environments for smart-contract work. (faucet.circle.com) The move gives developers a way to begin building and testing around cirBTC before any production rollout. Circle’s cirBTC product page says the token is “coming soon,” will be backed 1:1 by BTC, and is set to launch on Ethereum and Arc first. (faucet.circle.com) ### What exactly did Circle make available? Circle’s faucet page says developers can now request testnet cirBTC to “experiment with fund flows in your app or smart contract for free.” The same page lists Arc Testnet and Ethereum Sepolia among the supported networks for cirBTC testing. (faucet.circle.com) Circle’s developer docs also show Arc Testnet and Ethereum Sepolia in its supported testnet environments for Circle Contracts, the company’s smart-contract tooling. That places cirBTC’s first public test environment on the same two chains Circle has already highlighted for the asset’s eventual launch. (circle.com) ### Why are Arc and Ethereum the first test networks? Circle’s cirBTC page says the product is “launching on Ethereum & Arc first” and describes the asset as “architected for a multichain future.” The page also says cirBTC is intended to integrate with USDC, Arc and Circle Mint as part of a broader Circle-native stack. (faucet.circle.com) Arc has appeared across Circle’s recent developer materials as a growing part of its infrastructure push. Circle’s docs and release notes show Arc quickstarts and testnet support in adjacent products, including crosschain USDC tooling. (developers.circle.com) ### What is Circle saying cirBTC is for? Circle’s product page says cirBTC is designed for “institutional markets” and for users including OTC desks, market makers and lending protocols. The company says each cirBTC token will be backed 1:1 by native BTC and that reserves will be “readily and independently verifiable onchain.” (circle.com) The same page frames cirBTC as a neutral, interoperable wrapped-Bitcoin product rather than a token limited to a single chain. Circle says multichain support and crosschain mobility are core parts of the design. (developers.circle.com) ### What can developers do with the testnet right now? Circle’s faucet says users can request testnet cirBTC directly to a wallet, with a limit of one request per pairing of asset and test network every two hours. The faucet also links back to Circle’s docs, which serve as the main entry point for developers building with the company’s onchain products. (circle.com) Circle’s broader developer platform includes contracts, wallets and crosschain transfer tools, which suggests cirBTC testing is being placed inside an existing developer stack rather than as a standalone token experiment. (circle.com) That is an inference based on how Circle presents cirBTC alongside those products in its docs and product pages. ### What comes next before a full launch? Circle’s cirBTC landing page says the product is still “coming soon,” and the company is collecting interest through a waitlist. The page does not give a mainnet date, but it does say Ethereum and Arc will be the first launch chains. (faucet.circle.com) For now, the next concrete step is in the public test environment: developers can access cirBTC through Circle’s faucet on Arc Testnet and Ethereum Sepolia and use the company’s docs and tooling to build against it ahead of a production rollout. (faucet.circle.com) (circle.com) (developers.circle.com)