Identifies references to unknown Liquid [filters](/docs/api/liquid/filters).

## Examples

The following examples contain code snippets that either fail or pass this check.

### ✗ Fail

```liquid
{{ x | some_unknown_filter }}
```


### ✓ Pass


```liquid
{{ x | upcase }}
```


## Options

```yaml
UnknownFilter:
  enabled: true
  severity: error
```

| Parameter | Description |
| --- | --- |
| `enabled` | Whether this check is enabled. |
| `severity` | The [severity](https://shopify.dev/themes/tools/theme-check/configuration#check-severity) of the check. |

## Disabling this check

Disabling this check isn't recommended.