> 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/flashblocks/flashblocks-api/newflashblocktransactions-flashblocks.md).

# newFlashblockTransactions - Flashblocks

This subscribes to individual preconfirmed transactions as they land in Flashblocks. Each notification carries one transaction. Pass `true` as a second parameter to include full transaction objects with associated logs; omit or pass `false` to receive only transaction hashes. Lighter-weight than `newFlashblocks` when you only care about the transaction stream and not the full block state.

{% hint style="warning" %}
**WebSocket-only method.** This method requires the WebSocket transport at `wss://go.getblock.io/<ACCESS-TOKEN>/`. It will not work via HTTP POST. Preconfirmed events arrive at the Flashblock cadence — approximately every 200ms on Base, 250ms on Optimism.
{% endhint %}

## Parameters

| Parameter          | Type    | Required | Description                                                                             |
| ------------------ | ------- | -------- | --------------------------------------------------------------------------------------- |
| subscriptionType   | string  | Yes      | Must be `"newFlashblockTransactions"`                                                   |
| includeFullObjects | boolean | No       | `true` to receive full transaction objects with logs; `false` (default) for hashes only |

## Request Example

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

```bash
# WebSocket-only. Use wscat (or similar) to connect first:
wscat -c 'wss://go.getblock.io/<ACCESS-TOKEN>/'

# Then send:
{"jsonrpc": "2.0", "method": "eth_subscribe", "params": ["newFlashblockTransactions", true], "id": "getblock.io"}
```

{% endcode %}
{% endtab %}

{% tab title="JavaScript (Axios)" %}

```javascript
import WebSocket from 'ws';

const ws = new WebSocket('wss://go.getblock.io/<ACCESS-TOKEN>/');

ws.on('open', () => {
    ws.send(JSON.stringify({
    "jsonrpc": "2.0",
    "method": "eth_subscribe",
    "params": [
        "newFlashblockTransactions",
        true
    ],
    "id": "getblock.io"
}));
});

ws.on('message', (data) => {
    const msg = JSON.parse(data.toString());
    if (msg.method === 'eth_subscription') {
        // Preconfirmed data update
        console.log(msg.params.result);
    } else {
        // Subscription ID response
        console.log('Subscribed:', msg.result);
    }
});
```

{% endtab %}

{% tab title="Python (Requests)" %}

```python
import asyncio
import json
import websockets

async def main():
    async with websockets.connect('wss://go.getblock.io/<ACCESS-TOKEN>/') as ws:
        await ws.send(json.dumps({
    "jsonrpc": "2.0",
    "method": "eth_subscribe",
    "params": [
        "newFlashblockTransactions",
        true
    ],
    "id": "getblock.io"
}))
        async for message in ws:
            msg = json.loads(message)
            if msg.get('method') == 'eth_subscription':
                # Preconfirmed data update
                print(msg['params']['result'])
            else:
                # Subscription ID response
                print('Subscribed:', msg.get('result'))

asyncio.run(main())
```

{% endtab %}

{% tab title="Rust (Reqwest)" %}

```rust
use tokio_tungstenite::connect_async;
use tokio_tungstenite::tungstenite::Message;
use serde_json::json;
use futures_util::{SinkExt, StreamExt};

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let (mut ws_stream, _) = connect_async("wss://go.getblock.io/<ACCESS-TOKEN>/").await?;

    let payload = json!({
        "jsonrpc": "2.0",
        "method": "eth_subscribe",
        "params": [
                "newFlashblockTransactions",
                true
        ],
        "id": "getblock.io"
});
    ws_stream.send(Message::Text(payload.to_string())).await?;

    while let Some(msg) = ws_stream.next().await {
        println!("{:?}", msg?);
    }
    Ok(())
}
```

{% endtab %}
{% endtabs %}

## Response Example

{% code overflow="wrap" %}

```json
{
    "jsonrpc": "2.0",
    "id": "getblock.io",
    "result": "0x5c1de6a7b8c9d0e1f2a3b4c5d6e7f8a9"
}
```

{% endcode %}

## Response Parameters

| Field  | Type   | Description                                                                                                                                                 |
| ------ | ------ | ----------------------------------------------------------------------------------------------------------------------------------------------------------- |
| result | string | Hex-encoded subscription ID. Each subsequent notification carries either a transaction hash (default) or a full transaction object with logs (`true` param) |

## Use Cases

* Wallet infrastructure watching for a specific user's transactions to preconfirm
* Transaction-level analytics without the overhead of full block payloads
* Building activity feeds for accounts with sub-second latency
* Front-running detection at the sub-block level

## Error Handling

| Status Code | Error Message     | Cause                                          |
| ----------- | ----------------- | ---------------------------------------------- |
| 403         | Forbidden         | Missing or invalid `<ACCESS-TOKEN>`            |
| -32602      | Invalid params    | Request parameters are missing or malformed    |
| -32603      | Internal error    | Server-side error while processing the request |
| 429         | Too Many Requests | Rate limit exceeded for your plan              |
| -32600      | Invalid Request   | Subscription called over HTTP; use WebSocket   |

## SDK Integration

{% tabs %}
{% tab title="ethers.js" %}
{% code overflow="wrap" %}

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

const provider = new ethers.WebSocketProvider('wss://go.getblock.io/<ACCESS-TOKEN>/');

// Flashblocks subscription types aren't first-class in ethers — use the raw send interface:
const subscriptionId = await provider.send('eth_subscribe', ["newFlashblockTransactions", true]);
console.log('Subscribed:', subscriptionId);

// Listen for incoming events on the WebSocket transport
provider.websocket.addEventListener('message', (event) => {
    const msg = JSON.parse(event.data);
    if (msg.method === 'eth_subscription' && msg.params?.subscription === subscriptionId) {
        console.log('Flashblocks update:', msg.params.result);
    }
});
```

{% endcode %}
{% endtab %}

{% tab title="viem" %}

```javascript
import { createPublicClient, webSocket } from 'viem';

const client = createPublicClient({
    transport: webSocket('wss://go.getblock.io/<ACCESS-TOKEN>/')
});

// Flashblocks subscription types use the raw request interface:
const subscriptionId = await client.request({
    method: 'eth_subscribe',
    params: ["newFlashblockTransactions", true]
});
console.log('Subscribed:', subscriptionId);
```

{% 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/flashblocks/flashblocks-api/newflashblocktransactions-flashblocks.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.