Testnets Explained: What They Are and Why Sepolia Replaced Everything
What a testnet is, why Ethereum keeps retiring them, which ones are current, and why testnet tokens will never be worth anything.
Last reviewed 2026-09-14
What a testnet is
A parallel copy of a blockchain running the same software with worthless tokens. Contracts deployed there behave as they would on mainnet, so developers can find bugs before the bugs cost money. The tokens are handed out free by faucets precisely because they must have no value — the moment a test token acquires a price, the test environment stops being a test environment.
The current ones
| Network | Status | Notes |
|---|---|---|
| Sepolia | Current | The default Ethereum testnet for application developers |
| Holešky | Current | Larger validator set, aimed at staking and infrastructure testing |
| Hoodi | Current | Newer network for validator and protocol-upgrade testing |
| Goerli | Retired | Deprecated in 2023, no longer maintained |
| Ropsten, Rinkeby, Kovan | Long dead | Shut down after the merge |
| Mumbai | Dead | Replaced by Polygon Amoy |
Any tutorial still pointing at Goerli or Mumbai is out of date, and anything else it says should be treated with the same suspicion.
Why they keep getting retired
Two reasons. State bloat — a testnet accumulates junk over years until syncing one becomes painful — and the fact that Goerli’s test ETH developed a real secondary market price, which defeated the purpose entirely. Sepolia was designed with a permissioned validator set partly to prevent that recurring.
Layer 2 testnets
Each rollup runs its own: Arbitrum Sepolia, Base Sepolia, Optimism Sepolia, Linea Sepolia. They settle to Ethereum Sepolia, which is why the reliable way to fund them is to get Sepolia ETH once and bridge it, rather than hunting for an L2-specific faucet.
The part worth internalising
Testnet tokens have no value and never will. Nobody will buy your Sepolia ETH. A faucet asking for payment is a scam, a service offering to convert testnet tokens to real ones is a scam, and a “testnet airdrop” that wants a wallet signature is very likely a drainer.
What testnet activity is genuinely worth is participation records: several protocols have distributed real tokens to addresses that used their testnet meaningfully. That is a side effect of real testing, not a reason to farm.