Small Node.js demo repo showing how to:

• List UTXOs from a Bitcoin testnet node (listunspent)
• Build, sign, and broadcast a transaction (createrawtransaction, signrawtransactionwithwallet, sendrawtransaction)
• Monitor node status (getblockcount, getmempoolinfo)

• Bitcoin Core installed and available in your PATH
• A Bitcoin Core node running on testnet
• Node.js 18+
• Some testnet BTC in your wallet (grab from any available faucet)

1. Clone and install dependencies:

git clone <your-repo-url>
cd bitcoin-utxo-demo
yarn

2. Configure Bitcoin Core:

• Create/edit ~/.bitcoin/bitcoin.conf (Linux) or ~/Library/Application Support/Bitcoin/bitcoin.conf (Mac) or %APPDATA%\Bitcoin\bitcoin.conf (Windows).
• Example minimal config:

testnet=1
server=1

[test]
rpcuser=user
rpcpassword=pass
rpcallowip=127.0.0.1
rpcport=18332

3. Start your node:

yarn btc:start:daemon

4. Create and load a wallet:

yarn btc:wallet:create
yarn btc:wallet:load

5. Fund your testnet wallet from a faucet.

6. Copy .env.example to .env and set the recipient address:

TESTNET_RECIPIENT_ADDRESS=tb1qyourrecipientaddress...

# Explore UTXOs in your wallet
yarn explore

# Build & send a transaction (handles change automatically)
yarn build-tx

# Monitor node info
yarn monitor

yarn btc:start:daemon     # start node in background
yarn btc:start            # start node in foreground
yarn btc:stop             # stop node

yarn btc:wallet:create    # create test wallet
yarn btc:wallet:load      # load wallet
yarn btc:wallet:waitload  # retry loading wallet until ready

yarn btc:addr:new         # generate new address
yarn btc:balance          # check wallet balance
yarn btc:utxos            # list unspent outputs
yarn btc:status           # get blockchain status

• Fee and send amount are hardcoded in txBuilder.js (0.00001 BTC and 0.00004 BTC).
• Change outputs are automatically created, so your wallet balance is preserved after sending.
• This is a minimal demo — real wallets handle multiple UTXOs, dynamic fee estimation, and better change management.