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

# How to declare attributes for faceting with the API

> How to declare attributes for faceting with the API.

export const Index = () => <Tooltip tip="An Algolia index is a searchable dataset that consists of records and configuration settings. These settings define how the records are searched and ranked.">
    index
  </Tooltip>;

Algolia lets you create categories based on specific attributes so users can filter search results by those categories.
For example, if you have an <Index /> of books, you could categorize them by author and genre.
This allows users to filter search results by their favorite author or discover new genres.

To run the code examples on this page, [install the latest API client](/doc/libraries/sdk/install).

To enable this categorization,
declare the attributes `genre` and `author` as [`attributesForFaceting`](/doc/api-reference/api-parameters/attributesForFaceting):

<CodeGroup>
  ```cs C# theme={"system"}
  var response = await client.SetSettingsAsync(
    "INDEX_NAME",
    new IndexSettings
    {
      AttributesForFaceting = new List<string> { "genre", "author" },
    }
  );
  ```

  ```dart Dart theme={"system"}
  final response = await client.setSettings(
    indexName: "INDEX_NAME",
    indexSettings: IndexSettings(
      attributesForFaceting: [
        "genre",
        "author",
      ],
    ),
  );
  ```

  ```go Go theme={"system"}
  response, err := client.SetSettings(client.NewApiSetSettingsRequest(
    "INDEX_NAME",
    search.NewEmptyIndexSettings().SetAttributesForFaceting(
      []string{"genre", "author"})))
  if err != nil {
    // handle the eventual error
    panic(err)
  }
  ```

  ```java Java theme={"system"}
  UpdatedAtResponse response = client.setSettings(
    "INDEX_NAME",
    new IndexSettings().setAttributesForFaceting(Arrays.asList("genre", "author"))
  );
  ```

  ```js JavaScript theme={"system"}
  const response = await client.setSettings({
    indexName: 'INDEX_NAME',
    indexSettings: { attributesForFaceting: ['genre', 'author'] },
  });
  ```

  ```kotlin Kotlin theme={"system"}
  var response =
    client.setSettings(
      indexName = "INDEX_NAME",
      indexSettings = IndexSettings(attributesForFaceting = listOf("genre", "author")),
    )
  ```

  ```php PHP theme={"system"}
  $response = $client->setSettings(
      'INDEX_NAME',
      ['attributesForFaceting' => [
          'genre',

          'author',
      ],
      ],
  );
  ```

  ```python Python theme={"system"}
  response = client.set_settings(
      index_name="INDEX_NAME",
      index_settings={
          "attributesForFaceting": [
              "genre",
              "author",
          ],
      },
  )
  ```

  ```ruby Ruby theme={"system"}
  response = client.set_settings(
    "INDEX_NAME",
    Algolia::Search::IndexSettings.new(attributes_for_faceting: ["genre", "author"])
  )
  ```

  ```scala Scala theme={"system"}
  val response = Await.result(
    client.setSettings(
      indexName = "INDEX_NAME",
      indexSettings = IndexSettings(
        attributesForFaceting = Some(Seq("genre", "author"))
      )
    ),
    Duration(100, "sec")
  )
  ```

  ```swift Swift theme={"system"}
  let response = try await client.setSettings(
      indexName: "INDEX_NAME",
      indexSettings: IndexSettings(attributesForFaceting: ["genre", "author"])
  )
  ```
</CodeGroup>

Sometimes, you may have many facet values.
For instance, if you have a book index, you may also have a lot of different authors.
[The engine can't return more than 1,000 values per facet](/doc/api-reference/api-parameters/maxValuesPerFacet),
so if you have more than that, you may want to let your users search for them.
Do this by using the `searchable` modifier.

<CodeGroup>
  ```cs C# theme={"system"}
  var response = await client.SetSettingsAsync(
    "INDEX_NAME",
    new IndexSettings
    {
      AttributesForFaceting = new List<string> { "genre", "searchable(author)" },
    }
  );
  ```

  ```dart Dart theme={"system"}
  final response = await client.setSettings(
    indexName: "INDEX_NAME",
    indexSettings: IndexSettings(
      attributesForFaceting: [
        "genre",
        "searchable(author)",
      ],
    ),
  );
  ```

  ```go Go theme={"system"}
  response, err := client.SetSettings(client.NewApiSetSettingsRequest(
    "INDEX_NAME",
    search.NewEmptyIndexSettings().SetAttributesForFaceting(
      []string{"genre", "searchable(author)"})))
  if err != nil {
    // handle the eventual error
    panic(err)
  }
  ```

  ```java Java theme={"system"}
  UpdatedAtResponse response = client.setSettings(
    "INDEX_NAME",
    new IndexSettings().setAttributesForFaceting(Arrays.asList("genre", "searchable(author)"))
  );
  ```

  ```js JavaScript theme={"system"}
  const response = await client.setSettings({
    indexName: 'INDEX_NAME',
    indexSettings: { attributesForFaceting: ['genre', 'searchable(author)'] },
  });
  ```

  ```kotlin Kotlin theme={"system"}
  var response =
    client.setSettings(
      indexName = "INDEX_NAME",
      indexSettings = IndexSettings(attributesForFaceting = listOf("genre", "searchable(author)")),
    )
  ```

  ```php PHP theme={"system"}
  $response = $client->setSettings(
      'INDEX_NAME',
      ['attributesForFaceting' => [
          'genre',

          'searchable(author)',
      ],
      ],
  );
  ```

  ```python Python theme={"system"}
  response = client.set_settings(
      index_name="INDEX_NAME",
      index_settings={
          "attributesForFaceting": [
              "genre",
              "searchable(author)",
          ],
      },
  )
  ```

  ```ruby Ruby theme={"system"}
  response = client.set_settings(
    "INDEX_NAME",
    Algolia::Search::IndexSettings.new(attributes_for_faceting: ["genre", "searchable(author)"])
  )
  ```

  ```scala Scala theme={"system"}
  val response = Await.result(
    client.setSettings(
      indexName = "INDEX_NAME",
      indexSettings = IndexSettings(
        attributesForFaceting = Some(Seq("genre", "searchable(author)"))
      )
    ),
    Duration(100, "sec")
  )
  ```

  ```swift Swift theme={"system"}
  let response = try await client.setSettings(
      indexName: "INDEX_NAME",
      indexSettings: IndexSettings(attributesForFaceting: ["genre", "searchable(author)"])
  )
  ```
</CodeGroup>

If you only need the filtering feature, use `filterOnly` to reduce the index size and improve search speed.
For example, you could automatically filter what genre the users can search based on the section of your website they're on (without displaying genre as a clickable filter).

<CodeGroup>
  ```cs C# theme={"system"}
  var response = await client.SetSettingsAsync(
    "INDEX_NAME",
    new IndexSettings
    {
      AttributesForFaceting = new List<string> { "filterOnly(genre)", "author" },
    }
  );
  ```

  ```dart Dart theme={"system"}
  final response = await client.setSettings(
    indexName: "INDEX_NAME",
    indexSettings: IndexSettings(
      attributesForFaceting: [
        "filterOnly(genre)",
        "author",
      ],
    ),
  );
  ```

  ```go Go theme={"system"}
  response, err := client.SetSettings(client.NewApiSetSettingsRequest(
    "INDEX_NAME",
    search.NewEmptyIndexSettings().SetAttributesForFaceting(
      []string{"filterOnly(genre)", "author"})))
  if err != nil {
    // handle the eventual error
    panic(err)
  }
  ```

  ```java Java theme={"system"}
  UpdatedAtResponse response = client.setSettings(
    "INDEX_NAME",
    new IndexSettings().setAttributesForFaceting(Arrays.asList("filterOnly(genre)", "author"))
  );
  ```

  ```js JavaScript theme={"system"}
  const response = await client.setSettings({
    indexName: 'INDEX_NAME',
    indexSettings: { attributesForFaceting: ['filterOnly(genre)', 'author'] },
  });
  ```

  ```kotlin Kotlin theme={"system"}
  var response =
    client.setSettings(
      indexName = "INDEX_NAME",
      indexSettings = IndexSettings(attributesForFaceting = listOf("filterOnly(genre)", "author")),
    )
  ```

  ```php PHP theme={"system"}
  $response = $client->setSettings(
      'INDEX_NAME',
      ['attributesForFaceting' => [
          'filterOnly(genre)',

          'author',
      ],
      ],
  );
  ```

  ```python Python theme={"system"}
  response = client.set_settings(
      index_name="INDEX_NAME",
      index_settings={
          "attributesForFaceting": [
              "filterOnly(genre)",
              "author",
          ],
      },
  )
  ```

  ```ruby Ruby theme={"system"}
  response = client.set_settings(
    "INDEX_NAME",
    Algolia::Search::IndexSettings.new(attributes_for_faceting: ["filterOnly(genre)", "author"])
  )
  ```

  ```scala Scala theme={"system"}
  val response = Await.result(
    client.setSettings(
      indexName = "INDEX_NAME",
      indexSettings = IndexSettings(
        attributesForFaceting = Some(Seq("filterOnly(genre)", "author"))
      )
    ),
    Duration(100, "sec")
  )
  ```

  ```swift Swift theme={"system"}
  let response = try await client.setSettings(
      indexName: "INDEX_NAME",
      indexSettings: IndexSettings(attributesForFaceting: ["filterOnly(genre)", "author"])
  )
  ```
</CodeGroup>

**Don't include colons (`:`) in attribute names that you want to use for faceting because the [`filters`](/doc/api-reference/api-parameters/filters) syntax relies on that character as a delimiter.**

## See also

* [How to declare attributes for faceting in the dashboard](/doc/guides/managing-results/refine-results/faceting/how-to/declaring-attributes-for-faceting-with-dashboard)
* [Auto-selected facets](/doc/guides/solutions/ecommerce/filtering-and-navigation/tutorials/auto-selected-facets)
* [Guided search](/doc/guides/solutions/ecommerce/filtering-and-navigation/tutorials/guided-search)
* [Visual facets](/doc/guides/solutions/ecommerce/filtering-and-navigation/tutorials/visual-facets)