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

# GET /block/:hash/header

Returns the hex-encoded block header.

This method will use `10` [Compute Units](/nodeapi/about/billing).

***

## **Parameters**

**`block`**- block hash, required.

Example: `0000000000000000000226ab487ff1a8456a30feb1bde3d65b6a67128074e19a`

## Returns

Returns the hex-encoded block header.

The response from this endpoint can be cached indefinitely.

```text wrap theme={"theme":{"light":"github-light","dark":"github-dark-default"}}
0000ac2511730758cca9d49bb6cfb80f2e71a78208370d939a91010000000000000000008f4315a66896bb5e2ef5d3778d09e3f34ab568c16614832ddefafdc015eb4c96ab0d9f68b32c02174576cd9d
```

<CodeGroup>
  ```bash title="mainnet" theme={"theme":{"light":"github-light","dark":"github-dark-default"}}
  curl https://mainnet.bitcoin.validationcloud.io/v1/<YOUR_API_KEY_HERE>/block/0000000000000000000226ab487ff1a8456a30feb1bde3d65b6a67128074e19a/header \
   -X GET
  ```

  ```bash title="testnet" theme={"theme":{"light":"github-light","dark":"github-dark-default"}}
  curl https://testnet.bitcoin.validationcloud.io/v1/<YOUR_API_KEY_HERE>/block/0000000000000000000226ab487ff1a8456a30feb1bde3d65b6a67128074e19a/header \
   -X GET
  ```
</CodeGroup>


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