# Chains API

The Blocknative Chains API provides metadata on supported chains, including their chain ID, label, architecture, and available features. This allows developers to dynamically identify which networks are integrated with Blocknative services.

## Authentication <a href="#api-endpoint" id="api-endpoint"></a>

A valid Blocknative API key is OPTIONAL in the `Authorization` Header of every request. Request an API key [here](https://www.blocknative.com/request-api-key).

A free API key is recommended for more generous rate limits and future features.

## API Endpoint

<mark style="color:blue;">`GET`</mark> `https://api.blocknative.com/chains`

Returns a list of supported chains along with their chain ID, label, architecture (e.g., `evm`), and available features (e.g., `blockprices`). This allows users to identify networks where Blocknative provides gas price estimation and related services. The list and available fields are subject to change as new chains or parameters are added or updated.

## Rate Limits <a href="#rate-limits" id="rate-limits"></a>

Each endpoint is limited to provide updated results once per second for paid tier API keys, or every 5 seconds for free tier API keys. Polling faster than these rates may deliver stale data.

## **Example Request**

```bash
curl -H 'Authorization: optional-apikey-here'
     'https://api.blocknative.com/chains'
```

## **Headers**

| Name          | Type   | Description                                                |
| ------------- | ------ | ---------------------------------------------------------- |
| Authorization | String | <p>OPTIONAL</p><p>if used, must contain a valid apikey</p> |

## **Response Codes**

| Code  | Description                                     |
| ----- | ----------------------------------------------- |
| `200` | Success                                         |
| `401` | API key invalid or not provided                 |
| `429` | Rate limit exceeded. Refer to headers for retry |

### **Example Response**

```json
[
  {
    "arch": "evm",
    "chainId": 1,
    "label": "Ethereum",
    "features": ["blockprices", "recentblocks", "distribution"],
    "icon": "https://bnc-assets.com/evm/1/assets/icon.svg",
    "system": "ethereum",
    "network": "mainnet"
  },
  {
    "arch": "evm",
    "chainId": 137,
    "label": "Polygon",
    "features": ["blockprices"],
    "icon": "https://bnc-assets.com/evm/137/assets/icon.svg",
    "system": "ethereum",
    "network": "mainnet"
  },
  {
    "arch": "evm",
    "chainId": 8453,
    "label": "Base",
    "features": ["blockprices"],
    "icon": "https://bnc-assets.com/evm/8453/assets/icon.svg",
    "system": "ethereum",
    "network": "mainnet"
  }
]
```

### **Response Fields**

| Field      | Type           | Description                                                                                                                                                                             |
| ---------- | -------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `arch`     | String         | The blockchain architecture (e.g., `"evm"`).                                                                                                                                            |
| `chainId`  | Integer        | The unique identifier for the blockchain (e.g., `1` for Ethereum).                                                                                                                      |
| `label`    | String         | The human-readable name of the blockchain (e.g., `"Polygon zkEVM"`).                                                                                                                    |
| `features` | Array\[String] | List of features supported by Blocknative on this chain (e.g., `["blockprices"]`).                                                                                                      |
| `icon`     | String         | URL to the blockchain's icon.                                                                                                                                                           |
| `system`   | String         | The human-readable name of the ecosystem, (e.g.  `"ethereum"` or `"bitcoin"`)                                                                                                           |
| `network`  | String         | Internal name of the blockchain (e.g. `"mainnet"` or `"sepolia"`). See [chain table](https://docs.blocknative.com/gas-platform#gas-platform-currently-supports-the-following-networks). |

## **Notes**

* The list of supported blockchains and available features may change as new networks are integrated.
* This endpoint does not include gas price data—use the [`/blockprices`](https://docs.blocknative.com/gas-prediction/gas-platform) endpoint for real-time gas estimations.