> ## Documentation Index
> Fetch the complete documentation index at: https://docs.polygon.technology/llms.txt
> Use this file to discover all available pages before exploring further.

# Interact with a node RPC

> How to connect to a Polygon RPC provider and send your first blockchain request using Alchemy.

Most developers use a node provider rather than running their own full node. A node provider receives your requests and returns responses from the blockchain automatically, so you can focus on building.

This guide uses Alchemy as the RPC provider example.

## Prerequisites

* An [Alchemy account](https://alchemy.com/?r=e68b2f77-7fc7-4ef7-8e9c-cdfea869b9b5)
* Access to the [Alchemy Dashboard](https://dashboard.alchemyapi.io)

## Create an Alchemy API key

1. Navigate to the **Create App** button in the **Apps** tab.

   <img src="https://mintcdn.com/polygon-labs/PnA6B0XDAD7POEHb/img/tools/alchemy/getting-started.png?fit=max&auto=format&n=PnA6B0XDAD7POEHb&q=85&s=1e73fe9d5d320ef24ad1d6275262915c" alt="img" width="3584" height="1980" data-path="img/tools/alchemy/getting-started.png" />

2. Fill in the details under **Create App** to get your new key. You can also see the applications you previously made by you and your team on this page. Pull existing keys by clicking on **View Key** for any app.

   <img src="https://mintcdn.com/polygon-labs/PnA6B0XDAD7POEHb/img/tools/alchemy/create-app-details.png?fit=max&auto=format&n=PnA6B0XDAD7POEHb&q=85&s=7a00a59b315affe71b7fe4575420b4c4" alt="img" width="991" height="588" data-path="img/tools/alchemy/create-app-details.png" />

<Tip title="Optional">
  You can also pull existing API keys by hovering over **Apps** and selecting one. You can **View Key** here, as well as **Edit App** to whitelist specific domains, see several developer tools, and view analytics.
</Tip>

<div className="text-center">
  <img src="https://mintcdn.com/polygon-labs/PnA6B0XDAD7POEHb/img/tools/alchemy/alchemy-app-creation.gif?s=48dfc9d5273d3d8960c232bdb363e24d" alt="Alchemy App Creation GIF" width="600" height="339" data-path="img/tools/alchemy/alchemy-app-creation.gif" />
</div>

## Send a cURL request

You can interact with Alchemy's Polygon infrastructure using JSON-RPC from the command line.

Use `POST` requests with the `Content-Type: application/json` header. Pass your query as the `POST` body with these fields:

* `jsonrpc`: The JSON-RPC version. Only `2.0` is supported.
* `method`: The API method. See the [API reference](https://alchemyenterprisegroup.readme.io/reference/polygon-api-quickstart).
* `params`: A list of parameters to pass to the method.
* `id`: The ID of your request, returned in the response so you can match requests to responses.

```bash theme={null}
curl https://eth-mainnet.alchemyapi.io/jsonrpc/demo \
  -X POST \
  -H "Content-Type: application/json" \
  --data '{"jsonrpc":"2.0","id":73,"method":"eth_gasPrice","params":[]}'
```

<Note>
  To send requests to your own app instead of the public demo, replace `https://eth-mainnet.alchemyapi.io/jsonrpc/demo` with `https://eth-mainnet.alchemyapi.io/v2/your-api-key`.
</Note>

Expected response:

```json theme={null}
{ "id": 73,
  "jsonrpc": "2.0",
  "result": "0x09184e72a000" // 10000000000000 }
```

## Set up the Alchemy SDK

Use the Alchemy SDK to make blockchain requests directly from a JavaScript or Node.js dApp.

If you already use Web3.js or Ethers.js, change your node provider URL to an Alchemy URL with your API key: `https://eth-mainnet.alchemyapi.io/v2/your-api-key`

<Note>
  The scripts below must run in a **node context** or be **saved in a file**, not run directly from the command line.
</Note>

### Install the SDK

Create a project directory and install the package.

With Yarn:

```bash theme={null}
mkdir your-project-name
cd your-project-name
yarn init # (or yarn init --yes)
yarn add alchemy-sdk
```

With NPM:

```bash theme={null}
mkdir your-project-name
cd your-project-name
npm init   # (or npm init --yes)
npm install alchemy-sdk
```

### Create `index.js`

```js theme={null}
import { Alchemy, Network } from "alchemy-sdk";

const settings = {
  apiKey: "demo", // Replace with your Alchemy API key.
  network: Network.ETH_MAINNET, // Replace with your network.
};

const alchemy = new Alchemy(settings);

async function main() {
  const gasPrice = await alchemy.core.getGasPrice();
  console.log(gasPrice.toString());
}

main();
```

### Run

```bash theme={null}
node index.js
```