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Keccak-256 Hash via FastX402
x402
Keccak-256 Hash via FastX402 is a paid API for AI agents from fastx402.tools, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-17).
Computes the Keccak-256 (Ethereum-native SHA-3) hash of a UTF-8 string or hex-encoded bytes, returning the hex digest and input byte count.
Price / call$0.001
Success—
StatusUnknown
How this service works
146 pay-per-call tools for AI agents, from $0.001 per request in USDC on Base or Solana with x402. No account, no API key.
Output
A JSON object containing 'hash' (the 0x-prefixed 64-character Keccak-256 hex digest) and 'input_bytes' (the number of bytes consumed from the input), e.g. {"hash":"0x1c8aff...","input_bytes":5}.
Example use cases
Solidity event topic hash
“Give me the Keccak-256 hash of 'Transfer(address,address,uint256)' so I can use it as the event topic in my Ethereum log filter.”
Hash hex-encoded contract calldata
“Compute the Keccak-256 hash of the hex bytes 0x68656c6c6f and tell me how many bytes the input was.”
Verify smart contract function selector
“Hash the text 'approve(address,uint256)' with Keccak-256 — I want to check the first 4 bytes match the function selector in this transaction calldata.”
Technical details
Endpoint
GEThttps://fastx402.tools/keccak256?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need the Keccak-256 (Ethereum-native) variant of SHA-3 specifically — not standard SHA-3/FIPS-202, which uses different padding. Ideal for Ethereum development tasks such as computing event topic hashes, function selectors, address derivation checks, or any on-chain data verification. No API key or account required; payment is per-call via USDC on Base.
Side effects
- Missing both 'hex' and 'text' query params — server returns an error indicating input is required
- Malformed hex string (odd length or non-hex characters) — parsing error returned
- Payment not provided or insufficient — 402 Payment Required response before computation occurs
- Empty 0x input treated as empty bytes, returning the Keccak-256 of zero bytes
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"hash": "0x1c8aff950685c2ed4bc3174f3472287b56d9517b9c948127319a09a7a36deac8",
"input_bytes": 5
}
}Tags
x402
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