{"uid":"cap_W49V8t9lVc29FdfpMoCc3","slug":"ethereum-keccak256-hash-original-keccak-not-nist-sha3-bdfb4dab","name":"Ethereum Keccak256 Hash (Original Keccak, not NIST SHA3)","description":"Ethereum keccak256 — the original Keccak, not NIST SHA3 — Genesis402 / UnyKorn Operator Network","url":"https://twin.unykorn.org/hash-keccak256?utm_source=zero.xyz","method":"POST","headers":{},"bodySchema":{"type":"object","properties":{"params":{"type":"object","properties":{"hex":{"type":"string","pattern":"^0x[0-9a-fA-F]*$"},"text":{"type":"string","maxLength":49152}}}}},"responseSchema":{"type":"json","example":{"ok":true,"type":"hash-keccak256","receipt":{"tx_hash":"0x<64hex>","amount_usd":0.001,"receipt_id":"g402-<16hex>"},"generated_at":"<iso8601>"}},"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.001","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.001/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.001","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.001","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_Qxt9s3S9OUCZ6OsnN7OJW","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.001","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Computes the Ethereum-native Keccak256 hash (the original Keccak algorithm, not NIST SHA3) of a hex-encoded byte sequence or plain text string","exampleAgentPrompt":"Compute the Keccak256 hash (Ethereum-style, not NIST SHA3) of the text 'Transfer(address,address,uint256)' so I can get the ABI event topic signature.","exampleUseCases":[{"title":"ERC-20 event topic derivation","prompt":"Hash the string 'Transfer(address indexed from, address indexed to, uint256 value)' with Ethereum Keccak256 so I can use the result as the event topic selector in my log filter."},{"title":"Smart contract function selector","prompt":"I need the first 4 bytes of the Keccak256 hash of 'approve(address,uint256)' to build a raw Ethereum transaction calldata — can you compute that hash for me?"},{"title":"On-chain preimage verification","prompt":"Hash this hex data 0x48656c6c6f20576f726c64 using Ethereum Keccak256 so I can compare it against the stored hash in my smart contract and verify the preimage is correct."}],"resultDescription":"Returns a JSON object with ok=true, the type field set to 'hash-keccak256', the computed Keccak256 digest, a payment receipt including transaction hash, USD amount, and a unique receipt ID, and an ISO8601 timestamp of when the hash was generated.","failureModes":["Invalid hex input (not matching ^0x[0-9a-fA-F]*$ pattern) returns validation error","Text input exceeding 49152 characters rejected","Missing both hex and text parameters returns error","Payment failure via x402 protocol blocks execution","Malformed JSON body returns parse error"],"whenToPreferThis":"Choose this endpoint when you specifically need the original Ethereum Keccak256 algorithm (as used by Solidity, Web3, and EVM tooling) rather than the NIST-standardized SHA3-256, which produces different output for the same input. It is ideal for computing ERC-20/ERC-721 event topic hashes, Solidity function selectors, ENS label hashes, or any other on-chain hash that must match EVM behavior. Prefer this over general-purpose SHA3 libraries or endpoints when correctness against Ethereum's non-NIST variant matters.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-01T18:55:28.429Z","isFirstParty":false,"canonicalSlug":"ethereum-keccak256-hash-original-keccak-not-nist-sha3-bdfb4dab"}