Reverse-resolve a log event topic to its signature API

Reverse-resolves a 32-byte event topic hash (topic0 from an on-chain log) to its human event signature(s) via the 4byte directory, deduped and ordered by earliest registration (likely canonical). Fills the gap the catalog leaves: it can compute a topic FROM a signature and decode function calldata, but not turn an unknown LOG topic back into an event. Answers 'what event is 0xddf252ad...?'.

Price$0.01per request

MethodPOST

Route/v1/chain/fourbyte-decode-event

StatusLive

MIME typeapplication/json

Rate limit60/minute

Cache86400s public

chainevmeventtopic4bytedecodelogsignature

API URLhttps://x402.hexl.dev/v1/chain/fourbyte-decode-event

Integration docs

Example request

{
  "topic": "0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef"
}

Example response

{
  "topic": "0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef",
  "found": true,
  "best": {
    "signature": "Transfer(address,address,uint256)",
    "eventName": "Transfer",
    "firstSeen": "2020-11-30T22:38:00.801049Z"
  },
  "candidateCount": 1,
  "candidates": [
    {
      "signature": "Transfer(address,address,uint256)",
      "eventName": "Transfer",
      "firstSeen": "2020-11-30T22:38:00.801049Z"
    }
  ]
}

Input schema

{
  "type": "object",
  "required": [
    "topic"
  ],
  "properties": {
    "topic": {
      "type": "string",
      "description": "0x-prefixed 32-byte (64 hex) event topic hash (topic0)."
    }
  }
}

Output schema

{
  "type": "object",
  "additionalProperties": true
}