Testnet

A testnet runs the same or upcoming software as a main network, but on its own chain with its own blocks and tokens. Developers deploy contracts, test wallets and rehearse protocol upgrades there before touching mainnet. Test tokens are handed out for free through faucets, so mistakes cost nothing.

Sepolia is Ethereum's main public testnet for applications, and every Ethereum upgrade, including The Merge, has been run on testnets first. Bitcoin has its own testnet as well as signet. New projects often run incentivised testnets in which early users complete tasks in the hope of a future airdrop, which makes testnet activity a popular target for airdrop farming.

Testnet tokens should never be bought; anyone selling them is likely running a scam, and some sites posing as testnet tools are fronts for phishing that request approvals from real wallets. A smooth testnet run also does not guarantee a smooth launch, because real money attracts real attackers.