Testnet
A sandbox copy of a blockchain where developers trial code using tokens that hold no value.
Every serious blockchain runs a testnet alongside its mainnet. Ethereum has used several over the years, with Sepolia and Holesky the main ones in 2024. Test tokens come free from a faucet, so a bug costs nothing.
Testnets let teams break things safely. A smart contract that drains funds on testnet is a lesson; the same flaw on mainnet is a disaster. Most audits and upgrades pass through a testnet before going live.
Related terms
The live blockchain where transactions carry real economic value and tokens trade for actual money.
FaucetA service that hands out tiny amounts of crypto for free, mainly to fund testing on test networks.
Smart Contract AuditA structured review of contract code that hunts for vulnerabilities before attackers find and exploit them.