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  1. Home
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  5. Event Topic Generator

Event Topic Generator

Generate Ethereum event topic0 by hashing Solidity event signatures with keccak256. Supports direct signature input and ABI JSON parsing.

Read the guide

The event signature will be normalized to Transfer(address,address,uint256) before hashing.

Common Events

What is Event Topic0?

Event topic0 is the keccak256 hash of an event's signature. It uniquely identifies an event emitted by a smart contract. When a contract emits an event, topic0 is recorded on-chain, allowing indexers and wallets to filter and track event logs efficiently.

Example: Transfer Event

// Event in contract
event Transfer(address indexed from, address indexed to, uint256 value);

// Normalized signature (indexed removed)
Transfer(address,address,uint256)

// Topic0 (keccak256 hash)
0xddf252ad...

Why Use Event Topic0?

1

Event Filtering

Topic0 allows you to filter events by type on-chain and off-chain.

2

Unique Identification

Every event signature has a unique topic0 hash.

3

Indexing Performance

Queries for specific events are fast because topic0 is indexed.

Event Signature Normalization

Event signatures in Solidity can include parameter names and indexed keywords, but only the event name and parameter types matter for topic0 calculation:

// Original signature (with indexed and names)
Transfer(address indexed from, address indexed to, uint256 value)

// Normalized signature (types only)
Transfer(address,address,uint256)

// This normalized form is hashed to produce topic0

Frequently Asked Questions

Topic0 is the keccak256 hash of a Solidity event signature. It uniquely identifies the event type in Ethereum logs, making it easy to filter and search for specific events on the blockchain.

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