Dust

On Bitcoin, dust refers to outputs so small that spending them costs more in fees than they are worth. Bitcoin Core nodes refuse to relay transactions that create outputs below a dust threshold, a few hundred satoshis depending on the address type, to avoid clogging the UTXO set with unspendable crumbs. The threshold depends on fee policy, not on consensus rules.

Dust builds up naturally: rounding leftovers from exchanges, small rewards and faucet payouts. Many exchanges offer a button to convert small balances into their own token, and Bitcoin wallets can consolidate tiny outputs when fees are low. In account-based chains, dust usually means leftover token balances too small to bother moving.

Dust also has a hostile use. Attackers send tiny amounts to many addresses hoping owners will later spend them together with other coins, revealing links between addresses, or will interact with a malicious token. Wallets with coin control let users freeze such outputs instead of spending them.