What is a transaction hash (TXID)?

A transaction hash is the unique ID of one transaction on a blockchain. It is a long string of letters and numbers, created from the transaction's data when the transaction is made. You use it to look the transaction up, check whether it succeeded and show someone else exactly which transfer you mean.

What is a tx hash in crypto?

The terms transaction hash, tx hash, TXID and transaction ID usually mean the same thing. Etherscan describes it as a unique identifier generated whenever a transaction is made on Ethereum. Uniswap's support pages use the same definition and note that you can find it in your wallet or on an explorer.

The ID comes from a hash function, which turns data into a fixed-length fingerprint. Change one detail of the transaction and the hash changes completely. How that works is covered in what a hash is.

What is a TXID in Bitcoin?

In Bitcoin, the TXID is the result of running the raw transaction data through SHA-256 twice, often written HASH256. The result is 32 bytes, shown as 64 hexadecimal characters, using digits 0 to 9 and letters a to f.

One quirk is byte order. Learn Me A Bitcoin explains that block explorers display a TXID with its bytes reversed compared with how it appears inside raw transaction data. You will normally only see the display version.

Another detail involves SegWit. For SegWit transactions, the signature data is left out of the TXID calculation. That makes the ID harder to alter after a transaction is broadcast.

What does a TXID look like?

It depends on the chain:

• Bitcoin. 64 hex characters with no prefix, such as f4184fc596403b9d638783cf57adfe4c75c605f6356fbc91338530e9831e9e16.
• Ethereum and EVM chains. The same 64 hex characters with 0x in front, 66 characters in all. ethereum.org shows the example 0x97d99bc7729211111a21b12c933c949d4f31684f1d6954ff477d0477538ff017.
• Solana. Solana's docs say the first signature on a transaction, belonging to the fee payer, serves as the transaction ID. That is why Solana explorers often call it a signature rather than a hash, and it looks different from an Ethereum hash.

An Ethereum transaction hash and an Ethereum address both start with 0x, but an address is shorter. Pasting the right string into the right search box avoids confusion.

What is the tx hash used for?

The main uses are:

• Checking status. Etherscan shows whether a transaction succeeded or failed, its block, time, sender, receiver, value and fee. The steps are in how to use a blockchain explorer.
• Proving a payment. Sharing a TXID lets someone else confirm a transfer happened.
• Getting support. Exchanges and wallet teams ask for it when a deposit is missing. Uniswap suggests pasting the hash as text, not as a screenshot, so it can be read accurately. Common causes of delays are covered in why a crypto withdrawal is pending.

A TXID only points to public data. It cannot be used to move funds, so sharing it does not give anyone access to your wallet, though it does link the transaction to you for whoever sees it.