> 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/bitcoin-cash-bch/bitcoin-cash-json-rpc-api/preciousblock-bitcoin-cash.md).

# preciousblock - Bitcoin Cash

This method treats a block as if it were received before others with the same work, influencing which chain the node considers active during a tie.

## Parameters

| Parameter | Type   | Required | Description                               |
| --------- | ------ | -------- | ----------------------------------------- |
| blockhash | string | Yes      | The hash of the block to mark as precious |

## Request

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

```bash
curl --location --request POST 'https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/' \
--header 'Content-Type: application/json' \
--data-raw '{
    "jsonrpc": "2.0",
    "method": "preciousblock",
    "params": ["0000000000000000023a561e1ea370153aac5d1504726d1a039032831c05fcfc"],
    "id": "getblock.io"
}'
```

{% endcode %}
{% endtab %}

{% tab title="bitcoinjs-lib" %}
{% code title="example.js" %}

```javascript
const axios = require('axios');
const { data } = await axios.post('https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/', {
  jsonrpc: '2.0', method: 'preciousblock',
  params: ['0000000000000000023a561e1ea370153aac5d1504726d1a039032831c05fcfc'], id: 'getblock.io'
});
console.log(data.result);
```

{% endcode %}
{% endtab %}

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

```python
import requests

response = requests.post(
    'https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/',
    headers={'Content-Type': 'application/json'},
    json={
        'jsonrpc': '2.0',
        'method': 'preciousblock',
        'params': ["0000000000000000023a561e1ea370153aac5d1504726d1a039032831c05fcfc"],
        'id': 'getblock.io'
    }
)

print(response.json()['result'])
```

{% 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://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/")
        .header("Content-Type", "application/json")
        .json(&json!({
            "jsonrpc": "2.0",
            "method": "preciousblock",
            "params": ["0000000000000000023a561e1ea370153aac5d1504726d1a039032831c05fcfc"],
            "id": "getblock.io"
        }))
        .send()
        .await?
        .json::<Value>()
        .await?;

    println!("Result: {}", response["result"]);
    Ok(())
}
```

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

## Response

```json
{
    "error": null,
    "id": "getblock.io",
    "result": null
}
```

## Response Parameters

| Parameter | Type         | Description                                      |
| --------- | ------------ | ------------------------------------------------ |
| error     | null\|object | Error object when the call fails, otherwise null |
| id        | string       | Request identifier matching the request          |
| result    | null         | null on success                                  |

## Use Cases

* **Fork Resolution**: Prefer a specific block when two branches have equal work
* **Node Recovery**: Steer a node back onto the intended chain after a split
* **Testing**: Force chain selection in controlled test scenarios
* **Consensus Debugging**: Investigate reorg behaviour by biasing tip selection

## Error Handling

| Error Code | Message           | Description                                      |
| ---------- | ----------------- | ------------------------------------------------ |
| -8         | Invalid parameter | blockhash is not a valid 64-character hex string |
| -5         | Block not found   | No block with the given hash exists on this node |
| -32603     | Internal error    | Node failed to read the block from disk          |