# Transforming Data with Filters

You can transform an expression by providing one or more filters in the template expression. Filters are provided using the `|` pipe operator.

For example, to upper case the pet’s name:

```
I have one {{ @pet.type }} named {{ @pet.name | upper }}
```

Will produce the following:

```html
I have one cat named TIGER
```

{% hint style="info" %}
A complete [list of supported filters is available here](https://mozilla.github.io/nunjucks/templating.html#builtin-filters). 
{% endhint %}

Some filters accept arguments. To pass arguments to a filter, include the arguments list in parentheses: `filter(arg1, arg2, ...)`

Popular transformation filters are:

* `title`: convert text to Title Case
* `truncate`: truncate the text with ellipses. For example: `@description | truncate(10)` to truncate text to 10 characters.
* `join`: concatenate values using a separator. For example: `@names | join(",")`

{% hint style="info" %}
Under the hood, PixieBrix uses the popular [Nunjucks templating language](https://mozilla.github.io/nunjucks/), developed by the non-profit that makes the Firefox web browser!
{% endhint %}


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.pixiebrix.com/developing-mods/developer-concepts/text-template-guide/transforming-data-with-filters.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.