Event signature · Token standards

Transfer event signature and topic0

The topic0 of the Transfer event is 0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef, the keccak-256 hash of Transfer(address,address,uint256); 2 of its 3 arguments are indexed. Token moved between accounts.

Anatomy of a Transfer log

Topics

  • topic00xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3efkeccak256("Transfer(address,address,uint256)")
  • topic1from (address)indexed: filterable
  • topic2to (address)indexed: filterable

Data

  • datavalue (uint256)ABI-encoded, decoded with the ABI
Parameters

Arguments and where they sit in the log

Indexed arguments travel as topics and can be filtered cheaply; the others are ABI-encoded together in the data.

NameTypeIn the log
fromaddresstopic1
toaddresstopic2
valueuint256data

Solidity declaration

event Transfer(address indexed from, address indexed to, uint256 value);

Canonical signature

Transfer(address,address,uint256)

topic0

0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef

Ready-made alerts

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Who emits it

Contracts we list that emit Transfer

Any other contract with the same signature emits a log with the same topic0.

And 19 more contracts in the app's directory.

Code

Read Transfer logs in code

The same filter in viem, ethers and plain JSON-RPC, and the Solidity that emits it. The address is USD Coin (USDC), a contract we list that emits it.

viem
import { createPublicClient, http, parseAbiItem } from "viem"
import { mainnet } from "viem/chains"

const client = createPublicClient({ chain: mainnet, transport: http() })

const logs = await client.getLogs({
  address: "0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48",
  event: parseAbiItem("event Transfer(address indexed from, address indexed to, uint256 value)"),
  fromBlock: "latest",
})

for (const log of logs) console.log(log.args) // { from, to, value }
ethers v6
import { Interface, JsonRpcProvider } from "ethers"

const provider = new JsonRpcProvider(process.env.RPC_URL)
const iface = new Interface(["event Transfer(address indexed from, address indexed to, uint256 value)"])

const logs = await provider.getLogs({
  address: "0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48",
  topics: [iface.getEvent("Transfer")!.topicHash],
})

for (const log of logs) console.log(iface.parseLog(log)?.args)
JSON-RPC (eth_getLogs)
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "eth_getLogs",
  "params": [
    {
      "address": "0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48",
      "topics": [
        "0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef"
      ],
      "fromBlock": "latest"
    }
  ]
}
Solidity
event Transfer(address indexed from, address indexed to, uint256 value);

// inside a function:
emit Transfer(from, to, value);
Example

An example Transfer log, encoded and decoded

Placeholder values, not a real transaction: how each argument is stored in the topics and the data, and what decoding gives back.

Encoded (as the node returns it)
  • topic0keccak256("Transfer(address,address,uint256)")0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef
  • topic1from0x0000000000000000000000001111111111111111111111111111111111111111
  • topic2to0x0000000000000000000000002222222222222222222222222222222222222222
  • data0x0000000000000000000000000000000000000000000000000000000000000bb8
Decoded with the ABI
  • fromaddress · indexed0x1111111111111111111111111111111111111111
  • toaddress · indexed0x2222222222222222222222222222222222222222
  • valueuint2563000
FAQ

Frequently asked questions

What is the topic0 of the Transfer event?

0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef: the keccak-256 hash of Transfer(address,address,uint256).

Which Transfer arguments are indexed?

from, to are indexed and sit in the log's topics; value is in the data.

Do ERC-20 and ERC-721 Transfer events have the same topic0?

Yes. The signature is the same, so the hash is too. ERC-721 also indexes the third argument (the token id), so its logs carry four topics and an empty data field, where ERC-20 logs carry three topics and the amount in the data.

How do I get an alert when a contract emits Transfer?

Open one of the ready-made rules on this page, or add any contract and pick Transfer from the event list. Conditions can be set on indexed and non-indexed arguments, and each alert names the contract and links to the transaction.

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