Transaction hash

A transaction hash (often shortened to "tx hash" or "txid") is a unique

cryptographic fingerprint that identifies a single transaction on a

blockchain. The hash is derived from the transaction's contents, so any

change to the transaction would produce a different hash. Paste a tx hash at

tx.taxi/{hash} and you land on the configured explorer's transaction page

for that chain.

Format by chain

Tx hashes do not all look the same. The encoding follows whatever the chain

itself uses, which is what tx.taxi's classifier matches against when routing

a lookup.

• EVM chains (Ethereum, Base, Arbitrum, Optimism, Polygon, BSC, and

others) use a 32-byte Keccak-256 hash of the signed transaction, displayed

as a 0x-prefixed 64-character hex string. The same format applies whether

you are looking up a tx on ethereum,

base, or arbitrum one.

• Solana uses the transaction's first signature as its identifier. The

signature itself is a 64-byte Ed25519 signature, encoded as base58, which

typically renders as roughly 87 or 88 characters. Solana refers to this as

the "signature" rather than a "hash"; solana explorers

use it as the canonical transaction reference.

• UTXO chains (Bitcoin, Litecoin, Dogecoin, Bitcoin Cash, Dash, Zcash)

use a txid, which is the double-SHA256 of the serialized transaction.

The txid is 32 bytes, displayed as 64 hex characters with no 0x prefix.

See bitcoin for the canonical example.

Other ecosystems follow their own conventions. Tron, TON, Sui, Aptos, and

Cardano each have their own tx identifier formats, which the

chains index lists individually.

How explorers use it

When you supply a transaction hash to an explorer URL such as

/tx/{hash}, the explorer looks up the transaction by hash in its index and

renders the associated metadata: sender, recipient, value transferred, gas

or fee paid, status, and any logs or events emitted. On EVM chains the

explorer also fetches the transaction receipt,

which contains the post-execution status, the gas actually used, and decoded

event logs.

A tx hash is the most precise way to refer to a specific transaction. Block

height and address-based references can return many candidates, but a tx

hash always identifies at most one transaction on a given chain.

Common gotchas

• A tx hash exists from the moment a wallet signs and broadcasts a

transaction, but the explorer only resolves it once the tx is included in

a block. Before that, the tx sits in the mempool and

may show as "pending" or not appear at all.

• Two different chains can in theory return data for similar-looking hashes,

which is why tx.taxi requires you to pick the right chain (or relies on

format heuristics) before routing.

• A tx hash on its own does not tell you which chain the transaction ran on.

Same-format chains (all EVM L2s, for example) share a hash shape, so a

64-char hex string could refer to a tx on Ethereum, Base, Arbitrum, or any

other EVM rollup.

• If a tx is replaced (by a higher-nonce or higher-fee resend), its hash

changes. Replacement transactions are not the same transaction.