# GET /block/:hash/header

Returns the hex-encoded block header.

This method will use `10` [Compute Units](https://docs.validationcloud.io/v1/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.

{% code overflow="wrap" %}

```
0000ac2511730758cca9d49bb6cfb80f2e71a78208370d939a91010000000000000000008f4315a66896bb5e2ef5d3778d09e3f34ab568c16614832ddefafdc015eb4c96ab0d9f68b32c02174576cd9d
```

{% endcode %}

{% tabs %}
{% tab title="mainnet" %}

```bash
curl https://mainnet.bitcoin.validationcloud.io/v1/<YOUR_API_KEY>/block/0000000000000000000226ab487ff1a8456a30feb1bde3d65b6a67128074e19a/header \
 -X GET
```

{% endtab %}

{% tab title="testnet" %}

```bash
curl https://testnet.bitcoin.validationcloud.io/v1/<YOUR_API_KEY>/block/0000000000000000000226ab487ff1a8456a30feb1bde3d65b6a67128074e19a/header \
 -X GET
```

{% endtab %}
{% endtabs %}