Transaction ID (TXID)

A Transaction ID, or TXID, is a unique identifier assigned to every transaction on a blockchain. It is a fixed-length string of letters and numbers generated by running the transaction data through a cryptographic hash function. No two valid transactions produce the same TXID.

How a TXID Is Generated

When you send crypto, your wallet packages the transaction data: sender address, recipient address, amount, fee, and the cryptographic signature proving you authorized it. That data gets passed through a hash function, typically SHA-256 for Bitcoin or Keccak-256 for Ethereum. The result is the TXID.

The hash function is deterministic. Feed it the same transaction data and you always get the same output. Change a single character and the entire hash changes. This is what makes the TXID tamper-proof: any modification to the transaction would produce a completely different identifier.

A Bitcoin TXID looks like this: 4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b. It is 64 hexadecimal characters representing 32 bytes of data.

What You Can Do With a TXID

The TXID is your receipt. Any time you send or receive crypto and want to verify what happened, the TXID gives you access to the full transaction record on the blockchain.

Paste your TXID into a block explorer, and you can see the exact amount sent, the sending and receiving addresses, the fee paid, the block it was confirmed in, and the number of confirmations it has received. For Bitcoin, you use Mempool.space or Blockstream.info. For Ethereum, you use Etherscan.

• Proof of payment. When a merchant, exchange, or service asks you to confirm a transfer, send the TXID instead of a screenshot. It points directly to the on-chain record.
• Support disputes. If an exchange fails to credit your deposit, the TXID is the first thing their support team will request. It lets them locate the transaction without any ambiguity.
• Tracking confirmation status. Paste the TXID into a block explorer immediately after sending to watch your transaction move from the mempool to confirmed status in real time.

Where to Find Your TXID

Your wallet records every outbound transaction and shows the TXID in the transaction history. Most wallets display it as a clickable link that opens the transaction directly in a block explorer. If you received a payment, the sender can provide the TXID and you can independently verify the transaction arrived exactly as they described.

Sources

https://mempool.space
https://etherscan.io
https://learnmeabitcoin.com/technical/transaction/hash