How can I know which testnet am I on?

I just ran bitcoind -testnet, and I would assume it would connect to the most recent one, but is there a way to know it?

  • Bitcoin and bitcoind versions v0.3.14 - v0.3.19 used the first testnet.
  • Bitcoin, Bitcoin-Qt and bitcoind versions v0.3.20 - v0.6.1 used the second testnet.
  • Bitcoin-Qt and bitcoind version v0.7.0 and above use the third testnet.
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  • 1
    Oh, so it's hardcoded in the client, I didn't know that. – o0'. Jun 15 '13 at 20:37
  • 2
    The different testnets have slightly different rules, and a separate genesis block, so yes, they are hardcoded. No point in trying to support multiple versions. – Pieter Wuille Jun 16 '13 at 9:05

To double check, the genesis block for testnet3 (the current version as of this writing) has hash 000000000933ea01ad0ee984209779baaec3ced90fa3f408719526f8d77f4943. So with the daemon running, you can do

 bitcoind -testnet getblock 000000000933ea01ad0ee984209779baaec3ced90fa3f408719526f8d77f4943

If you are really on testnet3, you should see "height: 0" in the output.

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