A transaction ID (TXID) is the unique identifier of a TransactionTransactionA record of crypto moving from one wallet address to another, signed with the sender's private key and stored permanently on the blockchain. on a blockchain. It works like a receipt number: with it, anyone can find the transaction and see what happened to it.
How is it created?
The transaction ID is the HashHashA short fingerprint calculated from data, which changes completely if the data is altered by even a single character. of the transaction itself. On the Bitcoin network it is calculated with SHA-256 and is 64 characters long, made up of digits and the letters a to f. In practice, two different transactions never get the same ID.
Here, for example, is the transaction ID of a famous transaction from 22 May 2010, when the programmer Laszlo Hanyecz paid 10,000 bitcoin for two pizzas:
a1075db55d416d3ca199f55b6084e2115b9345e16c5cf302fc80e9d5fbf5d48d
On the Ethereum network, the ID is often called the transaction hash, and it starts with 0x.
When do you need one?
- To track a transfer. Paste the ID into a block explorerBlock explorerA website where anyone can look up transactions, wallet addresses and blocks on a blockchain. and you can see whether the transaction is still waiting in the MempoolMempoolThe holding area where unconfirmed transactions wait to get into a block; every node on the network keeps its own. or how many confirmationsConfirmationA sign that a transaction has been included in a block; each new block added on top counts as one more confirmation and makes it more secure. it has.
- When a transfer doesn't arrive. Crypto exchanges' support teams usually ask for the transaction ID when a deposit hasn't come through. It is the quickest way to find the transaction.
- As proof of payment. The ID shows that the payment was sent, to which wallet address and when.
What to keep in mind
It is safe to share a transaction ID, because it gives no access to your crypto. Bear in mind, though, that whoever has it can see the amount and the wallet addresses in the transaction, and trace them further.
Everything in Myntkaup Learn is written and regularly reviewed by the Myntkaup editorial team. It is for education and is not investment advice. Editorial policy. Updated 18 October 2026.