What does the --utxoindex flag do when running a Kaspa node?

The --utxoindex flag tells kaspad to calculate per-address balances and cache them so wallet operations can look them up. Without it, the node does not track how much KAS each address holds — it only processes and relays blocks. If you plan to check your balance or send KAS through the node, you need this flag; if you are only mining to the node and never need wallet functions, you can leave it out. For most beginners running a personal node, including --utxoindex is the right choice because it unlocks the full wallet experience.