Dust Transactions

Dust transactions are blockchain transactions that send or create very small amounts of cryptocurrency, known as dust. In Bitcoin and similar systems, an amount is usually called dust when it is so small that the transaction fee needed to spend it would be close to, or more than, the amount itself. Dust can build up naturally as leftover change from ordinary payments, but it is also created deliberately, by spammers, by marketers and by attackers trying to track or deceive wallet owners.

The idea is most closely tied to blockchains that use unspent transaction outputs (UTXOs), such as Bitcoin, where each payment creates separate coin pieces that must later be spent individually. Account-based chains such as Ethereum have their own versions, including tiny or zero-value token transfers used in scams. Dust transactions are related to, but broader than, the dusting attack, which is one specific malicious use.

Imagine a coin jar filling up with tiny copper coins that cost more to take to the bank than they are worth. They are still money, but spending them is not worth the trouble. Crypto dust is the same: small leftovers sitting in a wallet that would cost more in fees to move than they are worth.

Sometimes, though, a stranger drops a few of those tiny coins into someone's jar on purpose. The coins are harmless on their own, but if the owner later spends them together with their other money, the stranger may learn which jars belong to the same person, or may use the small gift as bait for a scam.

• Change from payments. When a wallet spends part of a coin, the remainder comes back as change, sometimes leaving very small outputs at a change address.
• Rising fees. An output that was worth spending when fees were low can become dust when network fees rise.
• Spam and promotion. In 2012 and 2013, the betting service Satoshi Dice sent many tiny Bitcoin outputs as part of its game, prompting complaints that it was bloating the blockchain. Others have sent dust to many addresses as a crude form of advertising.
• Deliberate tracking. Attackers send dust to many addresses and watch how it is spent, hoping to link addresses to one owner.
• Scam bait. Tiny transfers, or zero-value token transfers on account-based chains, can place a look-alike address in a victim's history, a tactic described under wallet address poisoning.

Bitcoin Core, the main Bitcoin software, applies a "dust limit" as a relay policy: by default, nodes do not relay transactions that create outputs below a threshold calculated from the cost of spending them. For a standard legacy address this works out at a few hundred satoshis, and the limit is lower for newer address types introduced with Segregated Witness. The rule is not part of Bitcoin's consensus rules, so miners can still include such transactions if they choose. In economic terms the useful threshold moves with fees. At a fee rate of 20 satoshis per virtual byte, spending a typical native SegWit input of about 68 virtual bytes costs roughly 1,360 satoshis, so any output smaller than that would lose money to spend; when fees fall to 2 satoshis per virtual byte, the same calculation gives about 136 satoshis. Other networks use minimum balances, account reserves or fees to make dust uneconomic. Because every UTXO must be stored by full nodes until spent, limiting dust helps keep the UTXO set, and therefore the cost of running a node, manageable.

The main risk from deliberate dust is to privacy. If a wallet automatically combines a dust output with the owner's other coins in a later transaction, it reveals that those addresses share an owner, information that firms specializing in blockchain analytics, and attackers, can use. In 2019, for example, the exchange Binance warned users after a large dusting campaign on the Litecoin network. Dust also adds to mempool congestion when sent in bulk. On networks such as Ethereum and Tron, scam dust often arrives as unknown tokens that direct the holder to a website that steals funds if they try to sell.

Many wallets let users freeze or hide individual UTXOs, a feature known as coin control, so that suspicious dust is never spent alongside other coins. Privacy-minded users avoid reusing addresses and may use techniques such as CoinJoin. Some exchanges offer to convert small leftover balances into a single main token. When fees are low, users can consolidate genuine small outputs into one larger output. The safest general advice is not to interact with unexpected tokens or tiny deposits and never to visit links attached to them. For very small payments that would otherwise create dust, users often prefer layer-two systems such as the Lightning Network, designed for microtransactions.