user68522: After I install the bitcoin core, it just sync the main net.   
Is there a way that I can also sync the test3 net for testing/developing purpose?

user48884: Start another instance of Bitcoin Core with the -testnet option to run it in testnet mode.

68522: <p>After I install the bitcoin core, it just sync the main net.   </p>

<p>Is there a way that I can also sync the test3 net for testing/developing purpose?</p>
 48884: <p>Start another instance of Bitcoin Core with the <code>-testnet</code> option to run it in testnet mode.</p>
