# Condition

**Condition** tags are useful for making decisions about what code to run, based on some specific value under inspection.

Often, condition tags are concerned with whether a value is **truthy** or **falsey**. In Liquid, only the values `false` and `nil` are falsey; all other values are truthy.

{% hint style="info" %}
For further discussion on how Liquid treats values, see their documentation: [Truthiness and falsiness in Liquid](https://shopify.dev/docs/themes/liquid/reference/basics/true-and-false).
{% endhint %}

## if

An `if` tag is always paired with an `endif` tag. The code between these tags only runs if the condition in the `if` tag evaluates to something truthy.

```liquid
{% if options.test_mode__boolean %}
  {% action "echo" summaries %}
{% endif %}
```

## unless

Identical in style to the `if` tag, the `unless` tag only executes the code it contains if the condition is falsey.

```liquid
{% unless options.default_tracking_url_template contains "TRACKING_NUMBER" %}
  {% error %}{{ "Placeholder 'TRACKING_NUMBER' is missing." | json }}{% enderror %}
{% endunless %}
```

## else

An `else` tag can be added within `if`, `unless`, and `case` blocks. The code that follows the `else` tag is run if the condition above it does not run.

```liquid
{% if customer.email != empty %}
  {% assign email = customer.email %}
{% else %}
  {% log "Customer had no email" %}
{% endif %}
```

```liquid
{% unless customer.email == empty %}
  {% assign email = customer.email %}
{% else %}
  {% log "Customer had no email" %}
{% endif %}
```

## elsif

An `elsif` tag adds a second condition to an `if` or `unless` block. If the condition above it does not run, the next `elsif` tag will be evaluated – and if its condition is truthy, the code that follows it will run.

Any number of `elsif` tags may be added within `if` or `unless` blocks.

```liquid
{% assign today = "tuesday" %}

{% if today == "monday" %}
  {% log "it's monday!" %}
{% elsif today == "tuesday" %}
  {% log "it's tuesday!" %}
{% endif %}
```

```liquid
{% assign today = "tuesday" %}

{% unless today == "tuesday" %}
  {% log "it's not tuesday!" %}
{% elsif today == "tuesday" %}
  {% log "it's tuesday!" %}
{% endif %}
```

## case, when

The `case` and `endcase` tag pair contain a series of `when` tags, and optionally an `else` tag. The value specified in the `case` tag is inspected, and Liquid then looks for a `when` tag that has a matching value. If one is found, that `when` tag gets to run its code. If no match is found, the code for the `else` tag (if given) is run.

```liquid
{% case order.cancel_reason    %}
  {% when "customer" %}
    {% assign cancel_reason = "It was the customer." %}
  {% when "fraud" %}
    {% assign cancel_reason = "It was fraud!" %}
  {% when "inventory" %}
    {% assign cancel_reason = "It was due to inventory issues." %}
  {% else %}
    {% assign cancel_reason = "It was something unknown." %}
{% endcase %}
```


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