# Filtering with Message Template Variables

## Overview

Message template variables in Welkin can be filtered and formatted to control how dynamic data appears in your communication templates. This is useful when you want to display a date in a specific format, truncate long text, or conditionally show values.

## What is Variable Filtering?

When you insert a variable like `{{patient.date_of_birth}}` into a message template, you can apply a filter to transform the output. Filters are appended to the variable using a pipe character (`|`).

**Syntax:**

```
{{variable_name | filter_name}}
```

## Common Filters

### Date Formatting

Format dates to display in a specific way:

```
{{patient.date_of_birth | date: "MM/DD/YYYY"}}
```

Supported formats: `MM/DD/YYYY`, `YYYY-MM-DD`, `Month DD, YYYY`

### Uppercase / Lowercase

```
{{patient.first_name | upcase}}
{{patient.last_name | downcase}}
```

### Default Value

Display a fallback when the variable is empty:

```
{{patient.phone | default: "No phone on file"}}
```

### Truncate

Limit the number of characters displayed:

```
{{patient.notes | truncate: 100}}
```

## Combining Filters

Multiple filters can be chained together:

```
{{patient.first_name | upcase | default: "Patient"}}
```

## Configuration

Variable filtering is configured directly in the message template editor in Designer. When adding a variable, use the filter syntax in the template body. Test templates using the preview functionality before publishing.

For basic variable usage, see [Filtering Message Template Variables](/designer/documents-and-assessments/filtering-message-template-variables.md).


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