Change Address
A change address is the address where leftover bitcoin is sent back to you in a transaction. Since UTXOs must be spent in full, the difference between the input amount and the payment plus fee is returned as change to an address you control.
How It Works
Bitcoin UTXOs work like physical bills — you cannot tear them in half. If you have a 1 BTC UTXO and want to send 0.3 BTC to someone, the entire 1 BTC UTXO is consumed as an input. The transaction creates two outputs: 0.3 BTC to the recipient and 0.6999 BTC back to you as change (with the remaining 0.0001 BTC going to the miner as a fee). The 0.6999 BTC output goes to a change address controlled by your wallet.
Modern HD wallets automatically generate fresh change addresses for every transaction, which is good for privacy. The change address is derived from the same seed phrase as all your other addresses, so it is covered by your existing backup. However, this automatic behavior can confuse users who see their transaction history showing sends to addresses they do not recognize. These are your change addresses — your wallet knows about them even if you do not.
From a privacy perspective, change addresses are one of the most analyzed aspects of Bitcoin transactions. Chain analysis firms use heuristics to identify which output is the payment and which is the change. Using round numbers for payments, having change amounts that match typical UTXO sizes, or always using the same address type all leak information. Verify change outputs on your hardware wallet screen to ensure your wallet is not being manipulated to send change to an attacker.
Key Points
- Leftover bitcoin from a UTXO spent in a transaction, returned to your own address
- HD wallets generate fresh change addresses automatically from your seed
- UTXOs must be spent in full — change is the difference minus fee
- Chain analysis firms use change output patterns to trace transactions
- Always verify change addresses on your hardware wallet display