These blockchains also exist on various testing networks ("testnet"), allowing developers to test their applications before deploying code on the main network ("mainnet").
As the below networks are for testing only, the USDC tokens in circulation on these networks are minted in a completely arbitrary way, and are in no way backed by real US dollars.
Ropsten is one of the Ethereum testing networks.
The USDC smart contract has been deployed to the Ropsten testnet and is available on address 0x07865c6e87b9f70255377e024ace6630c1eaa37f.
TestNet is the Algorand testing network.
The USDC Algorand Standard Asset (ASA) has been deployed to the TestNet and with asset ID 10458941.
Circle's sandbox environment is connected to USDC on the testing networks listed above.
In other words, when you send funds from a Circle hosted wallet to an external blockchain address, it will be sent as USDC on the testnet. Similarly, if you want to receive funds from an external blockchain address, you can use USDC on the testnet to achieve that.
Updated about 20 hours ago