TxID (Transaction ID)
A TxID (Transaction ID, or transaction hash) is the unique digital "receipt number" of every blockchain operation. It is a 64–88 character string that lets anyone look up a transaction in a public block explorer and verify its status, amount, sender, and recipient. TxID is the first piece of information a forensic analyst requests when investigating a crypto theft.
What a TxID is and how it is generated
Every blockchain transaction — a Bitcoin transfer, a USDT payment, or a smart contract interaction — receives a unique identifier at the moment it is created. The TxID (also called TXID, transaction hash, or tx hash) is generated by cryptographically hashing the full contents of the transaction. Change a single bit of data and the hash changes completely.
A TxID looks like this: 0x4a7b2c1e8f3d9a6b5c4e2d1f0e9b8a7c6d5e4f3a2b1c0d9e8f7a6b5c4d3e2f1a (Ethereum) or a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a9b0c1d2e3f4a5b6c7d8e9f0a1b2 (Bitcoin). This is not random — it is a mathematically derived fingerprint of the transaction.
How a TxID is generated
A TxID is produced by applying a SHA-256 hash function (double SHA-256 in Bitcoin) to the serialised transaction data. The inputs include: sender and recipient addresses, transfer amount, miner fee, timestamp, and the sender's cryptographic signature.
No two transactions will ever share the same TxID. Even sending the exact same amount to the same address one second later produces a completely different hash — because the timestamp and nonce have changed. This guarantees the uniqueness of every record on the blockchain.
How to find your transaction's TxID
In MetaMask: open Activity, find the transaction, click "View on Etherscan" — the TxID appears in the URL and in the Transaction Hash field. In Trust Wallet and most mobile wallets, tap any transaction in your history to see the hash.
On an exchange: go to Transaction History → Withdrawals → the TxID or Txid column. For older transactions, use the relevant block explorer — search by your sender address to list all associated transactions.
TxID formats across different blockchains
Bitcoin: 64 hex characters, no prefix. Example: a1b2c3d4.... Ethereum and all EVM-compatible networks (BSC, Polygon, Avalanche, Arbitrum): 66 characters with 0x prefix. Tron (TRC20): 64 Base16 characters. Solana: 88 Base58 characters — noticeably longer than others.
Block explorers by network: Bitcoin → mempool.space or blockchain.com; Ethereum → etherscan.io; BSC → bscscan.com; Tron → tronscan.org; Solana → solscan.io. Always tell support which network you are on — the same character string means something different on each chain.
Fake TxIDs — a common scam
A frequent scam: the fraudster sends a "payment confirmation" — a screenshot or text string claiming to be a TxID. Verifying it takes seconds: paste the string into the correct block explorer. If the transaction is not found, or shows a different amount or recipient, it is fabricated.
A related variant: a real TxID but with status "pending" or "failed." The seller claims funds were sent, but the transaction has zero confirmations. Always verify the status and confirmation count in the explorer before releasing anything.
TxID as an investigation tool
For forensic analysts, a TxID is the starting point of every investigation. From a single hash, an analyst can trace all subsequent wallet movements, identify address clusters belonging to one owner, and establish which exchange ultimately received the stolen funds.
One transaction can unlock an entire chain: through it, the analyst identifies the attacker's address, their exchange, their full transaction history, and — in many cases — a real person's identity through the platform's KYC records. That is why KarCrypto's first question is always: "Please provide the TxID of the transfer to the attacker."
Why TxID matters for your security
A TxID is the key element in resolving any dispute about a cryptocurrency transfer. Without it, you cannot prove a payment was sent, received, or lost. If an exchange claims it did not receive your deposit, the TxID will show exactly where the funds went and at which step they stopped.
Get into the habit of saving TxIDs for every important transfer. A simple spreadsheet — date, amount, network, TxID — takes seconds to maintain but can save hours when something goes wrong.
Frequently asked questions
How do I find my transaction TxID?
In most wallets, the TxID appears in transaction history. In MetaMask, click the transaction and select "View on Etherscan" — the TxID is in the URL. On an exchange, check the withdrawal history for the TxID column. For older transactions, search the block explorer by sender address.
Why can one transaction have multiple TxIDs?
This happens with replace-by-fee (RBF) in Bitcoin: if a transaction is stuck with a low fee, the wallet can broadcast a replacement with a higher fee using the same UTXO. Both versions get unique TxIDs, but only one is confirmed in the blockchain.
What does a "pending" transaction status mean?
Pending means the transaction was broadcast to the network but has not yet been included in a block. Miners process transactions by fee priority. During network congestion, this can take hours. Check status and confirmations in the block explorer by TxID.
Can I cancel a transaction using its TxID?
No — once a transaction is in a block, it is irreversible. Before the first confirmation, you can try Cancel Transaction in MetaMask (Ethereum) or replace-by-fee (Bitcoin) by broadcasting a new transaction with the same nonce and a higher fee.
Why does exchange support need my TxID?
A TxID is the only way to identify a specific transaction unambiguously. Support cannot locate a transfer by amount or date alone. With the TxID, they immediately see status, confirmation count, and sender and recipient addresses.