# fundrawtransaction - Bitcoin {diallowed}

This method adds inputs to a transaction until it has enough value to meet its output value. This will not modify existing inputs, and will add at most one change output to the transaction.

### Parameters

| Parameter                      | Type    | Required | Description                                                      |
| ------------------------------ | ------- | -------- | ---------------------------------------------------------------- |
| hexstring                      | string  | Yes      | The hex string of the raw transaction.                           |
| options                        | object  | No       | Options for funding.                                             |
| options.add\_inputs            | boolean | No       | Include inputs other than watch-only ones (default: true).       |
| options.changeAddress          | string  | No       | The Bitcoin address for receiving change.                        |
| options.changePosition         | number  | No       | The index of the change output.                                  |
| options.conf\_target           | number  | No       | Confirmation target in blocks.                                   |
| options.estimate\_mode         | string  | No       | Fee estimation mode: "unset", "economical", "conservative".      |
| options.fee\_rate              | number  | No       | Fee rate in sat/vB.                                              |
| options.includeWatching        | boolean | No       | Include inputs from watch-only addresses.                        |
| options.lockUnspents           | boolean | No       | Lock selected unspent outputs (default: false).                  |
| options.replaceable            | boolean | No       | Marks transaction as BIP125 replaceable.                         |
| options.subtractFeeFromOutputs | array   | No       | Array of output indexes to subtract fee from.                    |
| iswitness                      | boolean | No       | Whether the transaction hex is a serialized witness transaction. |

### Request

{% tabs %}
{% tab title="cURL" %}

```bash
curl --location --request POST 'https://go.getblock.io/<ACCESS-TOKEN>/' \
--header 'Content-Type: application/json' \
--data-raw '{
    "jsonrpc": "2.0",
    "method": "fundrawtransaction",
    "params": ["0200000001...00000000", {"conf_target": 6, "replaceable": true}],
    "id": "getblock.io"
}'
```

{% endtab %}

{% tab title="Axios" %}

```javascript
import axios from 'axios';

const data = JSON.stringify({
    "jsonrpc": "2.0",
    "method": "fundrawtransaction",
    "params": ["0200000001...00000000", {"conf_target": 6, "replaceable": true}],
    "id": "getblock.io"
});

const config = {
    method: 'post',
    url: 'https://go.getblock.io/<ACCESS-TOKEN>/',
    headers: {
        'Content-Type': 'application/json'
    },
    data: data
};

axios(config)
    .then(response => console.log(JSON.stringify(response.data)))
    .catch(error => console.log(error));
```

{% endtab %}

{% tab title="Request" %}

```python
import requests
import json

url = "https://go.getblock.io/<ACCESS-TOKEN>/"

payload = json.dumps({
    "jsonrpc": "2.0",
    "method": "fundrawtransaction",
    "params": ["0200000001...00000000", {"conf_target": 6, "replaceable": True}],
    "id": "getblock.io"
})

headers = {
    'Content-Type': 'application/json'
}

response = requests.post(url, headers=headers, data=payload)
print(response.text)
```

{% endtab %}

{% tab title="Rust" %}

```rust
use reqwest::header;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let client = reqwest::Client::new();
    
    let response = client
        .post("https://go.getblock.io/<ACCESS-TOKEN>/")
        .header(header::CONTENT_TYPE, "application/json")
        .body(r#"{
            "jsonrpc": "2.0",
            "method": "fundrawtransaction",
            "params": ["0200000001...00000000", {"conf_target": 6, "replaceable": true}],
            "id": "getblock.io"
        }"#)
        .send()
        .await?;
    
    println!("{}", response.text().await?);
    Ok(())
}
```

{% endtab %}
{% endtabs %}

### Response

```json
{
    "jsonrpc": "2.0",
    "id": "getblock.io",
    "result": {
        "hex": "0200000002074a0bfaf4462cef0a5665b89fd7fd5e...",
        "fee": 0.00001234,
        "changepos": 1
    }
}
```

### Response Parameters

| Field     | Type   | Description                                             |
| --------- | ------ | ------------------------------------------------------- |
| hex       | string | The resulting funded raw transaction hex.               |
| fee       | number | Fee in BTC the transaction will pay.                    |
| changepos | number | The position of the added change output, or -1 if none. |

### Use Case

The `fundrawtransaction` method is essential for:

* Automatically selecting UTXOs for transactions
* Adding change outputs to transactions
* Building transactions with optimal fee rates
* Creating RBF-enabled transactions
* Simplifying transaction construction workflows
* Supporting complex payment scenarios

### Error Handling

| Status Code | Error Message      | Cause                                               |
| ----------- | ------------------ | --------------------------------------------------- |
| 403         | Forbidden          | Missing or invalid ACCESS-TOKEN.                    |
| -4          | Insufficient funds | Not enough funds available to fund the transaction. |
| -22         | TX decode failed   | The transaction hex is malformed.                   |

### Integration Notes

The `fundrawtransaction` method helps developers:

* Build automated UTXO selection
* Create fee-optimal transactions
* Implement change address management
* Support coin control features
* Build batch payment systems


---

# Agent Instructions: 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:

```
GET https://docs.getblock.io/api-reference/bitcoin-btc/btc_fundrawtransaction.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
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.