UTXO Dust

Overview

What it means and why it exists

UTXO dust describes Bitcoin outputs whose small value makes them uneconomical or unevaluable under certain network relay policies relative to the cost of spending them. 'Dust' is not a fixed universal satoshi amount.

How it works

A node's dust rules estimate whether a typical future spend would cost a disproportionate fee. Scripts and relay-fee settings affect the threshold; some specialized outputs have different treatment. Wallets may avoid creating dust outputs and may combine small UTXOs when economical.

Technical details worth understanding

A payment of a few hundred satoshis can be larger or smaller than the applicable dust threshold depending on script and policy. 'Dust attack' has a separate privacy meaning, where tiny deposits are sent to recipients to encourage later address-linking when spent. A merchant's minimum acceptable payment is a business policy distinct from node relay dust rules.

What can go wrong

Dust thresholds belong mainly to transaction relay and standardness policy, not a universal rule that all small balances cease to exist. High future feerates can make otherwise valid outputs practically uneconomical to spend. Never treat unsolicited dust as proof of a legitimate customer payment.

Practical checks

Apply wallet or node dust rules using the actual output script and current relevant policy, not a single global satoshi number copied from a blog. Decide separately whether a small unsolicited deposit merits investigation or exclusion from invoice matching. High feerates can make otherwise valid outputs unattractive to spend.

Related concepts

Crypto Wallet, Private Key, Non-Custodial Wallet.

Further reading

Bitcoin Developer Guide — Wallets.