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

# Chain Status

> Query configured blockchain chains and their availability

## Overview

The chain status endpoint provides information about all blockchain chains configured in your Lasso RPC instance.

## Endpoint

```
GET /api/chains
```

## Response

Returns a JSON object containing an array of configured chains:

<ResponseField name="chains" type="array" required>
  Array of chain configuration objects

  <Expandable title="chain properties">
    <ResponseField name="chain_id" type="string" required>
      The numeric chain ID as a string (e.g., "1" for Ethereum Mainnet)
    </ResponseField>

    <ResponseField name="name" type="string" required>
      Human-readable name of the blockchain
    </ResponseField>

    <ResponseField name="chain_name" type="string" required>
      Internal identifier used in API paths and configuration
    </ResponseField>

    <ResponseField name="supported" type="boolean" required>
      Whether this chain is currently supported (always `true` for configured chains)
    </ResponseField>
  </Expandable>
</ResponseField>

## Response Example

```json theme={null}
{
  "chains": [
    {
      "chain_id": "1",
      "name": "Ethereum Mainnet",
      "chain_name": "ethereum",
      "supported": true
    },
    {
      "chain_id": "137",
      "name": "Polygon",
      "chain_name": "polygon",
      "supported": true
    },
    {
      "chain_id": "42161",
      "name": "Arbitrum One",
      "chain_name": "arbitrum",
      "supported": true
    }
  ]
}
```

## Use Cases

### Discover Available Chains

Query which chains are configured and ready to use:

```bash theme={null}
curl http://localhost:4000/api/chains
```

### Validate Chain Configuration

Check if a specific chain is configured before making RPC requests:

```bash theme={null}
# Check if Ethereum is configured
chains=$(curl -s http://localhost:4000/api/chains)
has_ethereum=$(echo $chains | jq '.chains[] | select(.chain_name=="ethereum") | .chain_id')

if [ -n "$has_ethereum" ]; then
  echo "Ethereum is configured with chain_id: $has_ethereum"
fi
```

### Dynamic Client Configuration

Use this endpoint to dynamically configure multi-chain applications:

```javascript theme={null}
const response = await fetch('http://localhost:4000/api/chains');
const { chains } = await response.json();

// Build RPC endpoints for each chain
const rpcEndpoints = chains.reduce((acc, chain) => {
  acc[chain.chain_name] = `http://localhost:4000/rpc/${chain.chain_id}`;
  return acc;
}, {});

console.log(rpcEndpoints);
// {
//   ethereum: 'http://localhost:4000/rpc/1',
//   polygon: 'http://localhost:4000/rpc/137',
//   arbitrum: 'http://localhost:4000/rpc/42161'
// }
```

## Chain Name vs Chain ID

Lasso RPC supports referencing chains by both their numeric `chain_id` and their `chain_name`:

* **chain\_id**: Standard EVM chain identifier (e.g., `1`, `137`, `42161`)
* **chain\_name**: Human-friendly identifier used in configuration files (e.g., `ethereum`, `polygon`, `arbitrum`)

Both can be used in RPC endpoint paths:

```bash theme={null}
# Using chain_id
curl -X POST http://localhost:4000/rpc/1 \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","method":"eth_blockNumber","params":[],"id":1}'

# Using chain_name (if supported by your configuration)
curl -X POST http://localhost:4000/rpc/ethereum \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","method":"eth_blockNumber","params":[],"id":1}'
```

## Notes

* The list of chains is determined by your configuration file
* All returned chains have `supported: true` as unsupported chains are not included in the response
* Chain configurations are loaded at startup and do not change without restarting the instance
* This endpoint is useful for service discovery in multi-chain applications