Set up a Bitcoin node

To cast spells on Bitcoin you need a Bitcoin Core node. This guide sets one up on testnet4.

Bitcoin Core

Bitcoin Core v30.0 or later is recommended (testnet4 was added in v28.0). Spell transactions carry a larger OP_RETURN than the historical 80-byte standardness limit, and current Bitcoin Core versions relay them. Install with Homebrew:

brew install bitcoin

Use this configuration (bitcoin.conf):

server=1
testnet4=1
txindex=1
addresstype=bech32m
changetype=bech32m

bitcoin.conf is usually located at:

macOS: ~/Library/Application Support/Bitcoin/bitcoin.conf
Linux: ~/.bitcoin/bitcoin.conf

Start bitcoind and let it sync.

Load a wallet

b createwallet testwallet  # create a wallet (you might already have one)
b loadwallet testwallet    # bitcoind does not load wallets automatically at startup

Get test BTC

Get a new address and fund it from a faucet:

b getnewaddress            # prints a new address

Visit https://mempool.space/testnet4/faucet and send test BTC to that address. Get at least 50,000 sats (0.0005 test BTC). Aim for more than one UTXO — tap the faucet a few times, or send sats within your own wallet so you have some small UTXOs and at least one larger one (≥ 10,000 sats).

jq

Several examples use jq:

brew install jq

Next steps

Cast your first spell — prove, sign, and broadcast on testnet4.