How to Get Bitcoin Testnet Coins?

I found out that the same mnemonic gives me two addresses on testnet: tb1pfscdjh8dkqy98gp0xkudrkx88zwslsvd32z60d9nhpm343rewsmqf55g7q and tb1q84jq2rq4jdf8nauum7haneseaqmg89zj944x5k. I can get test coins at the second one, but the first one doesn’t work. Why is that? How can I actually get testnet coins?

You can hit up testnet faucets. But some of them are kinda dead now. That second address is a Taproot one, and most faucets haven’t adjusted to send coins there yet.

A single mnemonic can create tons of addresses, not just two. BIP32 and BIP39 let you generate a whole bunch of them. Plus, yeah, as OmegaStarScream pointed out, that second one is Taproot. Most faucets won’t send to that type yet.

The main way to get testnet coins is through those faucets. Or, you could ask a friend for some or even send coins from one address to another if you have them. But honestly, why do you need multiple addresses for testnet coins?

Most faucets like testnet.coinfaucet.eu should work, but they might have issues sometimes. Just remember, they usually won’t send to Taproot addresses. If you wanna use a Taproot address, find a wallet that supports sending test coins there.

Can I mine test coins? I got some mining rigs.

Yeah, you can mine testnet coins. Just keep in mind, with the block height so high, the rewards are tiny right now... like 0.012 or something. Honestly, just grab coins from a faucet and then send ‘em to your Taproot address. Or you could play around with RegTest.