Testnets Shield Blockchain Protocols from Catastrophic Bugs

A testnet is a separate blockchain network that mirrors a production chain's rules and functionality but uses tokens with no monetary value.

Developers use testnets to deploy and interact with smart contracts exactly as they would on mainnet, testing function calls, simulating user interactions, measuring gas consumption, and verifying error handling works correctly.

Ethereum has run multiple testnets over its history, with Sepolia and Holesky serving as the primary public testing environments as of 2026 after the deprecation of Goerli.