Comparison of the different TestNets

Question

The Metamask client allows access to three test networks:

• Ropsten
• Kovan
• Rinkeby

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

• PoW
• Supported by geth and parity
• Best reproduces the current production environment
• Chaindata size 15 GB - Apr 2018

Kovan

• PoA (Immune to spam attacks)
• Supported by parity only
• Chaindata size 13 GB - Apr 2018

Rinkeby

• PoA (Immune to spam attacks)
• Supported by geth only
• Chaindata size 6 GB - Apr 2018

Sokol

• PoA (Immune to spam attacks)
• Supported by parity only
• Chaindata size 5gb - Jun 2018

If you need support on both geth and parity go wtih Ropsten. Otherwise choose Kovan, Sokol or Rinkeby as they are more stable.

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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 both geth and parity.
  • 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 --testnet or geth --networkid 3
  • parity --chain 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: parity --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 or geth --networkid 4
• Explorer https://rinkeby.etherscan.io/
• Github https://github.com/ethereum/EIPs/issues/225
• Website https://www.rinkeby.io

Sokol

• PoA testnet started by the POA.network team
• History:
  • Started in December 2017. Named after a subway station in Moscow.
• 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: 77
• Block time: 5 seconds
• Explorer https://sokol-explorer.poa.network/
• Public faucet: https://faucet-sokol.herokuapp.com/
• RPC endpoint: https://sokol.poa.network
• Wiki: https://github.com/poanetwork/wiki/wiki/POA-Network-Resources
• Github https://github.com/poanetwork/poa-chain-spec/tree/sokol

Görli

• Clique PoA testnet started by the Parity team
• 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 soon Parity as work is in progress)
• Cons:
  • It's still fresh and unstable.
  • Not all clients support it for the moment.
• Chain id: 6284
• Network id: 6284
• Block time: 15 seconds on average
• Status Dashboard: https://stats.goerli.net/ or http://ethstats.goerli.ethberl.in:3000/
• Explorer https://blockscout.com/eth/goerli/ or https://explorer.goerli.net/
• Github https://github.com/goerli/testnet

Answer 2

There are other 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
• 1: Expanse, an alternative Ethereum implementation, chain ID 2
• 2: Morden, the public Ethereum testnet, now Ethereum Classic testnet
• 3: Ropsten, the public cross-client Ethereum testnet
• 4: Rinkeby, the public Geth Ethereum testnet
• 42: Kovan, the public Parity Ethereum testnet
• 77: Sokol, the public POA testnet
• 99: POA, the public Proof of Authority Ethereum network
• 7762959: Musicoin, the music blockchain