> For the complete documentation index, see [llms.txt](https://docs.getblock.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.getblock.io/api-reference/ethereum-eth/web3_sha3-ethereum.md).

# web3\_sha3 - Ethereum

This method returns the Keccak-256 (SHA3-256) hash of the given hex-encoded data. Commonly used to compute event signature topics, function selectors, and content-addressable identifiers off-chain in a way that's guaranteed to match on-chain behavior.

## Parameters

| Parameter | Type   | Required | Description                                 |
| --------- | ------ | -------- | ------------------------------------------- |
| `data`    | string | Yes      | Hex-encoded data to hash (with `0x` prefix) |

## Request

{% tabs %}
{% tab title="cURL" %}
{% code overflow="wrap" %}

```bash
curl --location --request POST 'https://go.getblock.io/<ACCESS-TOKEN>/' \
--header 'Content-Type: application/json' \
--data-raw '{
    "jsonrpc": "2.0",
    "method": "web3_sha3",
    "params": [
        "0x68656c6c6f20776f726c64"
    ],
    "id": "getblock.io"
}'
```

{% endcode %}
{% endtab %}

{% tab title="Axios" %}
{% code title="example.js" %}

```javascript
const axios = require('axios');

const response = await axios.post('https://go.getblock.io/<ACCESS-TOKEN>/', {
    jsonrpc: '2.0',
    method: 'web3_sha3',
    params: [
        "0x68656c6c6f20776f726c64"
    ],
    id: 'getblock.io'
}, {
    headers: { 'Content-Type': 'application/json' }
});

console.log(response.data.result);
```

{% endcode %}
{% endtab %}

{% tab title="Request" %}
{% code title="example.py" %}

```python
import requests

response = requests.post(
    'https://go.getblock.io/<ACCESS-TOKEN>/',
    headers={'Content-Type': 'application/json'},
    json={
        'jsonrpc': '2.0',
        'method': 'web3_sha3',
        'params': [
        "0x68656c6c6f20776f726c64"
    ],
        'id': 'getblock.io'
    }
)

print(response.json())
```

{% endcode %}
{% endtab %}

{% tab title="Rust" %}
{% code title="example.rs" %}

```rust
use reqwest::Client;
use serde_json::{json, Value};

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let client = Client::new();
    
    let response = client
        .post("https://go.getblock.io/<ACCESS-TOKEN>/")
        .header("Content-Type", "application/json")
        .json(&json!({
            "jsonrpc": "2.0",
            "method": "web3_sha3",
            "params": [
        "0x68656c6c6f20776f726c64"
    ],
            "id": "getblock.io"
        }))
        .send()
        .await?
        .json::<Value>()
        .await?;
    
    println!("Result: {}", response["result"]);
    Ok(())
}
```

{% endcode %}
{% endtab %}
{% endtabs %}

## Response

```json
{
    "jsonrpc": "2.0",
    "id": "getblock.io",
    "result": "0x47173285a8d7341e5e972fc677286384f802f8ef42a5ec5f03bbfa254cb01fad"
}
```

## Response Parameters

| Parameter | Type   | Description                                               |
| --------- | ------ | --------------------------------------------------------- |
| `jsonrpc` | string | JSON-RPC protocol version ("2.0")                         |
| `id`      | string | Request identifier matching the request                   |
| `result`  | string | Keccak-256 hash of the input data, hex-encoded (32 bytes) |

## Use Cases

* **Event Signature Hashing**: Compute the `keccak256` hash of an event signature (e.g. `Transfer(address,address,uint256)`) to derive its topic0 for log filtering
* **Function Selector Derivation**: Compute the 4-byte function selector from a canonical signature for ABI encoding
* **ENS Name Hashing**: Hash ENS labels as part of computing an ENS namehash off-chain
* **Content Addressing**: Generate deterministic hashes for use as identifiers in IPFS-adjacent workflows or Merkle tree construction

## Error Handling

| Error Code | Message        | Description                              |
| ---------- | -------------- | ---------------------------------------- |
| -32602     | Invalid params | Input is not a valid hex-encoded string  |
| -32603     | Internal error | Node hashing subsystem returned an error |

## Web3 Integration

{% tabs %}
{% tab title="Ethers.js" %}
{% code title="ethers-example.js" %}

```javascript
import { ethers } from 'ethers';

// Ethers.js v6 exposes keccak256 directly — no RPC round-trip needed for
// off-chain hashing. This is the recommended path.
const hash = ethers.keccak256('0x68656c6c6f20776f726c64');
console.log(hash);

// For RPC-parity verification against the node:
const provider = new ethers.JsonRpcProvider('https://go.getblock.io/<ACCESS-TOKEN>/');
const nodeHash = await provider.send('web3_sha3', ['0x68656c6c6f20776f726c64']);
console.log(nodeHash);
```

{% endcode %}
{% endtab %}

{% tab title="Viem" %}
{% code title="viem-example.js" %}

```javascript
import { createPublicClient, http, keccak256 } from 'viem';
import { mainnet } from 'viem/chains';

// Viem exposes keccak256 directly — no RPC round-trip needed.
const hash = keccak256('0x68656c6c6f20776f726c64');
console.log(hash);

// For RPC-parity verification against the node:
const client = createPublicClient({
    chain: mainnet,
    transport: http('https://go.getblock.io/<ACCESS-TOKEN>/'),
});

const nodeHash = await client.request({
    method: 'web3_sha3',
    params: ['0x68656c6c6f20776f726c64'],
});
console.log(nodeHash);
```

{% endcode %}
{% endtab %}
{% endtabs %}


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.getblock.io/api-reference/ethereum-eth/web3_sha3-ethereum.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.