What a nonce is in blockchain transactions
A nonce is a per-account counter that orders and identifies each transaction on account-based blockchains like Ethereum; a gap stalls the ones that follow.
Vahe HakobyanEditor-in-chief
Updated Oct 5, 20263 min readFact-checked
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Not every blockchain works this way, but on account-based networks the number is part of the payment itself. Most wallets set it for you, so it stays out of sight until a payment gets stuck.
How does a nonce keep transactions in order?
Each address runs its own count, and the number rises by one as each payment confirms. A transaction can confirm only when its nonce is the next unused one for that address. Nodes may hold a future nonce, but they will not confirm it ahead of the missing ones.
- A future nonce waits in a queue.
- A gap holds back every later transaction.
- Filling the missing slot releases the queued ones.
What happens if a nonce is wrong?
A too-low nonce points at a slot the account has already filled, so nodes reject the payment. A too-high nonce is usually queued until the earlier numbers confirm. The payment settles only once the count catches up with it.
How do you replace a stuck transaction?
Send a new transaction that reuses the same nonce, and the network keeps only one of the two. On Ethereum, a replacement needs a higher gas price, often at least ten percent higher, not just a bigger total fee.
A replacement works only while the original is pending. Once it confirms, that nonce is spent.
Transaction nonce vs mining nonce
The two numbers share a name and nothing else. A transaction nonce tracks one account's payments, while a mining nonce is a value a miner changes in a block header until the hash meets the target.
Frequently asked questions
Only one can confirm, because the account count moves a single step. The other is dropped rather than treated as a second payment.
Not in one you have already broadcast. Wallets can replace it with a new transaction using the same nonce, or cancel it with a zero-value transfer to your own address.
No. Account-based chains such as Ethereum use them, while Bitcoin tracks unspent outputs instead.
Your wallet usually reads it and shows it before you confirm. A block explorer also lists the transaction count for the address.
