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

# customThemeId

> Specifies the custom theme to use in the resulting embed session. Used to apply your own custom styles.

<Tip>
  To use a default Omni theme, use the [`theme`](/embed/setup/url-parameters/theme).
</Tip>

In the **Embed URL Builder**, this is the **Custom theme ID** field.

## Syntax

```markdown theme={null}
customThemeId=<theme_id>
```

## Properties

<ParamField path="customThemeId" type="string">
  A valid theme ID from your Omni instance.
</ParamField>

## Examples

```markdown wrap title="Example customThemeId" theme={null}
customThemeId=abcdefgh-ijkl-mnop-qrst-123456789123
```