UTXO stands for Unspent Transaction Output. It is the data structure Bitcoin uses to track ownership. Instead of maintaining account balances, Bitcoin tracks discrete chunks of value that have been received in transactions but not yet spent.
Every Bitcoin transaction consumes one or more UTXOs as inputs and produces one or more new UTXOs as outputs. When the network sees a valid signature spending an existing UTXO, that UTXO is marked spent and the new UTXO it created becomes available for the recipient to spend later.
Your wallet's "balance" is not stored anywhere on the blockchain. Your wallet software calculates it by scanning every UTXO that can be spent with a key you control and adding them up. A wallet with three UTXOs of 0.5, 0.3, and 0.2 BTC has a balance of 1.0 BTC, but those three chunks are tracked separately.
Ethereum and most other blockchains use the account model: each address has a single balance number that gets debited and credited. Bitcoin's UTXO model is more like physical cash. If you owe someone $7 and you have only a $10 bill, you hand over the $10 and receive $3 in change. Bitcoin transactions work the same way: to spend 0.5 BTC when your only UTXO is 0.7 BTC, the transaction consumes the full 0.7 UTXO and produces two new UTXOs (0.5 to the recipient, 0.2 back to you minus fees).
This design is harder to reason about but enables better privacy (you can split UTXOs across many addresses), parallel transaction validation (UTXOs are independent), and cleaner pruning (spent UTXOs can be discarded from working memory).
For users: understanding UTXOs explains why Bitcoin transactions sometimes have unexpected change outputs and why fees scale with the number of inputs. For developers: building on Bitcoin requires UTXO-aware coin selection algorithms, since picking which UTXOs to spend affects fees and privacy. For analysts: UTXO age distribution (the "HODL waves" chart) is a powerful on-chain metric for measuring long-term holder behavior.
The BTC Network panel on the TerminalFeed dashboard shows mempool size in transactions, which directly maps to pending UTXO movements. Our mempool guide walks through how transactions and UTXOs flow into blocks. The Whale Watch surfaces large UTXO movements as they happen.