Comparison of the different TestNets

Question

The Metamask client allows access to four test networks:

• Ropsten
• Kovan
• Rinkeby
• Goerli

I'm curious:

• What are the similarities / differences between them?
• Which use cases are best for each network
• Are there more than these listed above?

Answer 1

Ropsten

• Proof-of-Work (Ethash)
• Supported by Geth, Besu, and all other Ethereum clients
• Best reproduces the current Ethereum production environment
• Chaindata size 15 GB - Apr 2018

Kovan

• Proof of Authority (Authority Round)
• Supported by OpenEthereum and Nethermind only
• Chaindata size 13 GB - Apr 2018

Rinkeby

• Proof of Authority (Clique)
• Supported by Geth, Besu, Nethermind, and OpenEthereum
• Chaindata size 6 GB - Apr 2018

Goerli

• Proof of Authority (Clique)
• Supported by Geth, Besu, Nethermind, and OpenEthereum
• Chaindata size 0 GB - Apr 2018

If you need a stable testnet with support on multiple clients go with Goerli. If you need to have conditions as close as possible to mainnet, but less stability than Goerli, choose Ropsten.

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Detailed version below:

Ropsten

• PoW testnet
• History:
  • Started in November 2016. Named after a subway station in Stockholm.
  • Was DoS attacked in February 2017 which made synching slow and made clients consume a lot of disk space.
  • Was revived in March 2017 and became usable again.
• Pros:
  • Best reproduces the current production environment, i.e. system and network conditions on the live Ethereum mainnet, because it's PoW net.
  • Can be used with all clients.
  • Ether can be mined. Or requested from a faucet:
    • https://faucet.metamask.io/
    • http://faucet.ropsten.be:3001
    • https://faucet.bitfwd.xyz/
    • What public test-networks and faucets exist?
• Cons:
  • Not immune to spam attacks. Because of this it's less stable.
• Network id: 3
• Block time: sub-30 seconds
• Commands:
  • geth --ropsten
  • besu --network ropsten
• Explorer https://ropsten.etherscan.io/
• Github https://github.com/ethereum/ropsten

Kovan

• PoA testnet started by the Parity team
• History:
  • Started in March 2017. Named after a subway station in Singapore.
• Pros:
  • Immune to spam attacks (as Ether supply is controlled by trusted parties)
• Cons:
  • Not supported in Geth.
  • Doesn't fully reproduce the current production environment as it uses PoA.
  • Ether can't be mined. It has to be requested from the faucet.
• Network id: 42
• Block time: 4 seconds
• Command: openethereum --chain kovan
• Explorer https://kovan.etherscan.io/
• Github https://github.com/kovan-testnet/proposal

Rinkeby

• PoA testnet started by the Ethereum team. Uses Clique PoA consensus protocol.
• History:
  • Started in April 2017. Named after a metro station in Stockholm.
• Pros:
  • Immune to spam attacks (as Ether supply is controlled by trusted parties)
• Cons:
  • Supported by Geth only
  • Doesn't fully reproduce the current production environment as it uses PoA.
  • Ether can't be mined. It has to be requested from a faucet:
    • https://faucet.rinkeby.io/
• Network id: 4
• Block time: 15 seconds
• Command: geth --rinkeby
• Explorer https://rinkeby.etherscan.io/
• Github https://github.com/ethereum/EIPs/issues/225
• Website https://www.rinkeby.io

Görli

• Clique PoA testnet started by the Goerli Initiative
• History:
  • Started in November 2018 after a proposal by Afri. It's a testnet that has the goal of being both widely usable across all client implementations supporting Clique PoA engine (EIP-225), and robust enough to guarantee consistent availability and high reliability.
• Pros:
  • Supported by multiple clients (including Geth, Pantheon, Nethermind and Open Ethereum)
• Chain id: 5
• Network id: 5
• Block time: 15 seconds on average
• Status Dashboard: https://stats.goerli.net/
• Explorer https://goerli.etherscan.io/
• Github https://github.com/goerli/testnet
• Website https://www.goerli.net

Answer 2

There are other (test-)networks as well, as described in this SO answer, copied here with their network id numbers:

• 0: Olympic, Ethereum public pre-release testnet
• 1: Frontier, Homestead, Metropolis, the Ethereum public main network
• 1: Classic, the (un)forked public Ethereum Classic main network, chain ID 61
• 2: Morden, the public Ethereum testnet, now Ethereum Classic testnet (retired)
• 3: Ropsten, the public proof-of-work Ethereum testnet
• 4: Rinkeby, the public Geth Ethereum testnet
• 5: Goerli, the fresh cross-client Ethereum testnet
• 42: Kovan, the public OpenEthereum testnet
• 77: Sokol, the public POA testnet
• 99: POA, the public Proof of Authority Ethereum network