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

# getBlockHeader

> Retrieves the block header for the specified Beacon Chain block ID.

### Parameters

<ParamField query="chainId" type="string" default="toncoin-testnet" required>
  Unique identifier for a blockchain network.
</ParamField>

<ParamField body="id" type="number" default={1} required>
  Request identifier used to match responses.
</ParamField>

<ParamField body="jsonrpc" type="string" default="2.0" required>
  JSON-RPC version.
</ParamField>

<ParamField body="method" type="string" default="getBlockHeader" required>
  JSON-RPC method name.
</ParamField>

<ParamField body="params" type="object" default={["finalized"]} placeholder="[&#x22;finalized&#x22;]" required>
  Parameters for getBlockHeader: \[block\_id]

  Positional parameters for <code>getBlockHeader</code>:

  <ul>
    <li><code>params\[]</code>: Block identifier: "head", "genesis", "finalized", a slot number, or a hex-encoded block root.</li>
  </ul>
</ParamField>

### Returns

<ResponseField name="result" type="object">
  Object containing the requested signed block header and its canonical status.

  <Expandable title="properties">
    <ResponseField name="root" type="string">
      The block root of the returned header.
    </ResponseField>

    <ResponseField name="canonical" type="boolean">
      Whether this header is part of the canonical chain.
    </ResponseField>

    <ResponseField name="header" type="object">
      Signed beacon block header.

      <Expandable title="properties">
        <ResponseField name="message" type="object">
          <Expandable title="properties">
            <ResponseField name="slot" type="string" />

            <ResponseField name="proposer_index" type="string" />

            <ResponseField name="parent_root" type="string" />

            <ResponseField name="state_root" type="string" />

            <ResponseField name="body_root" type="string" />
          </Expandable>
        </ResponseField>

        <ResponseField name="signature" type="string">
          BLS signature of the block header.
        </ResponseField>
      </Expandable>
    </ResponseField>
  </Expandable>
</ResponseField>

<RequestExample>
  ```bash Curl theme={null}
  curl --request POST \
    --url https://api.uniblock.dev/uni/v1/json-rpc?chainId=toncoin-testnet \
    --header 'content-type: application/json' \
    --data '{
      "id": 1,
      "jsonrpc": "2.0",
      "method": "getBlockHeader",
      "params": [
        "finalized"
      ]
    }'
  ```
</RequestExample>

<ResponseExample>
  ```json Success theme={null}
  {
    "jsonrpc": "2.0",
    "id": 1,
    "result": {
      "root": "0xabc123abc123abc123abc123abc123abc123abc123abc123abc123abc123abc1",
      "canonical": true,
      "header": {
        "message": {
          "slot": "123456",
          "proposer_index": "42",
          "parent_root": "0xparentroot...",
          "state_root": "0xstateroot...",
          "body_root": "0xbodyroot..."
        },
        "signature": "0xsignature..."
      }
    }
  }
  ```
</ResponseExample>