---
title: UnknownFilter
description: Identifies references to unknown filters.
source_url:
  html: >-
    https://shopify.dev/docs/storefronts/themes/tools/theme-check/checks/unknown-filter
  md: >-
    https://shopify.dev/docs/storefronts/themes/tools/theme-check/checks/unknown-filter.md
api_name: liquid
---

# Unknown​Filter

Identifies references to unknown Liquid [filters](https://shopify.dev/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.

***