# Using Apollo Explorer

Apollo Explorer is an online GraphQL playground you can use to run queries and subscribe to real-time updates from **Kadindexer**.

Access it here: [Apollo Explorer Sandbox](https://studio.apollographql.com/sandbox/explorer), and follow the steps below.

### Step 1: Open the Settings Panel

Once the page loads, click the **Settings** button in the top-left corner.

img
### Step 2: Set the API Endpoint

In the **Connection Settings**, choose the endpoint based on the network you want to query:

| Network | API Endpoint |
|  --- | --- |
| Mainnet | https://api.mainnet.kadindexer.io/v1 |
| Testnet | https://api.testnet.kadindexer.io/v1 |


Paste the selected URL into the **Endpoint** field:

img
### Step 3: Add Your API Key

Authorize access to the API by adding your previously generated API key.
Set it as the `x-api-key` header, as shown below:

img
### Step 4: Configure Subscriptions (Optional)

To enable real-time subscriptions, use the WebSocket endpoint for the network you’re connecting to:

| Network | WebSocket Endpoint |
|  --- | --- |
| Mainnet | wss://mainnet01.kadindexer.io/graphql |
| Testnet | wss://testnet04.kadindexer.io/graphql |


Paste the URL into the **Subscriptions** field:

img
### Step 5: Run Your First Query

You’re now ready to execute queries in Apollo Explorer. Here’s a simple example to get the latest block height through all chains in kadena blockchain:


```graphql
query {
  lastBlockHeight
}
```

img
✅ **Tip:** Once everything is configured, you can use Apollo Explorer to explore the schema, test queries, and subscribe to real-time blockchain events effortlessly.