> For the complete documentation index, see [llms.txt](https://docs.getblock.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.getblock.io/api-reference/filecoin-fil/native-api/filecoin_statelookupid.md).

# Filecoin.StateLookupID - Filecoin

Example code for the Filecoin.StateLookupID JSON RPC method. Complete guide on how to use Filecoin.StateLookupID JSON RPC in GetBlock Web3 documentation.

This method returns the short ID address (f0...) for a given address at a tipset. ID addresses are compact and stable, and are used internally by the chain.

{% hint style="info" %}
Many state methods take a tipset key as their final parameter: an array of block CIDs identifying the tipset to read. Pass an empty array `[]` to read against the current chain head.
{% endhint %}

## Parameters

| Parameter | Type   | Required | Description                                             |
| --------- | ------ | -------- | ------------------------------------------------------- |
| address   | string | Yes      | The address to resolve (f1/f2/f3/f4)                    |
| tipsetKey | array  | Yes      | Tipset key to read from; empty array for the chain head |

## Request

{% tabs %}
{% tab title="cURL" %}
{% code overflow="wrap" %}

```bash
curl --location --request POST 'https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/' \
--header 'Content-Type: application/json' \
--data-raw '{"jsonrpc": "2.0", "method": "Filecoin.StateLookupID", "params": ["f1ne72cbn6r55wea7ifjv4ypyti7t2df5dumsjhzq", []], "id": "getblock.io"}'
```

{% endcode %}
{% endtab %}

{% tab title="JavaScript" %}
{% code title="example.js" %}

```javascript
const response = await fetch('https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/', {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({
        jsonrpc: '2.0',
        method: 'Filecoin.StateLookupID',
        params: ["f1ne72cbn6r55wea7ifjv4ypyti7t2df5dumsjhzq", []],
        id: 'getblock.io'
    })
});

const data = await response.json();
console.log(data.result);
```

{% endcode %}
{% endtab %}

{% tab title="Python" %}
{% code title="example.py" %}

```python
import requests

response = requests.post(
    'https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/',
    headers={'Content-Type': 'application/json'},
    json={
        'jsonrpc': '2.0',
        'method': 'Filecoin.StateLookupID',
        'params': ["f1ne72cbn6r55wea7ifjv4ypyti7t2df5dumsjhzq", []],
        'id': 'getblock.io'
    }
)

print(response.json()['result'])
```

{% endcode %}
{% endtab %}
{% endtabs %}

## Response

```json
{
    "jsonrpc": "2.0",
    "id": "getblock.io",
    "result": "f0123456"
}
```

## Response Parameters

| Field  | Type   | Description                                  |
| ------ | ------ | -------------------------------------------- |
| result | string | The ID address (f0...) for the input address |

## Use Cases

* **Address Normalization**: Resolve any address to its ID form
* **Indexing Keys**: Use the stable ID address as a key
* **Deduplication**: Detect that two addresses are the same actor
* **State Queries**: Use ID addresses in downstream calls

## Error Handling

| Error Code | Message         | Description                                                 |
| ---------- | --------------- | ----------------------------------------------------------- |
| -32602     | Invalid params  | A parameter is missing or has the wrong type or format      |
| 1          | Actor not found | The address or actor does not exist in the requested tipset |
| -32603     | Internal error  | The node failed to process the request                      |