> For the complete documentation index, see [llms.txt](https://help.impact.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.impact.com/brand/what-would-you-like-to-learn-about/platform-features/promo-codes/regular-expression/regex-explained.md).

# Regex Explained

Regex (or Regular Expression) is a code that you can use to match text for a general case and is useful when matching promo codes. Regex is case-sensitive, so be sure to set your regex up in the case that matches your promo codes.

* There are three main logic cases for regex and promo codes: `starts with`, `ends with`, and `contains`.
* For this example, the base of our promo code is `SUMMER`.

{% tabs %}
{% tab title="Starts with" %}
You’ve issued a range of summer promo codes to partners, `SUMMER20OFF`, `SUMMER10`, and `SUMMER25`. We want to match them all to credit our partners, how do we go about it? We would use the `starts with` logic. Simply add a period and a star at the end of your base promo code.

The regex should be exactly `^(SUMMER).*`

This will automatically match any promo codes starting with `SUMMER` and ending with any other characters. Any codes not starting with `SUMMER` will not be matched.
{% endtab %}

{% tab title="Ends with" %}
You’ve issued a range of summer promo codes to partners, `20OFFSUMMER`, `10SUMMER`, and `25SUMMER` where the promo code always ends in `SUMMER`. How do we match them? We would use the `ends with` logic. Simply add a period and a star at the beginning of your base promo code and add a $ to specify the anchor of your string.

The regex should be exactly `^.*(SUMMER)$`

This will automatically match any promo codes starting with other characters and ending with `SUMMER`. Any codes not ending with `SUMMER` will not be matched.
{% endtab %}

{% tab title="Contains" %}
You’ve issued a range of summer promo codes to partners, `20SUMMER`, `SUMMER20OFF`, and `EXTRASUMMER10`, where `SUMMER` appears somewhere in the code. We would use the `contains` logic. Add `.*` before and after your base promo code, and wrap the expression in the ^ and $ anchors.

The regex should be exactly `^.*(SUMMER).*$`

This regex matches a promo code containing `SUMMER` anywhere in the code. Any codes that do not contain `SUMMER` will not be matched.
{% endtab %}
{% endtabs %}

For more complicated expressions, please reach out to your CSM or [contact support](https://app.impact.com/support/portal.ihtml?createTicket=true\&accountType=ADVERTISER) for help.

{% hint style="success" %}
**Note:** You can remove regex case sensitivity by adding `(?i)` after `^` in your regex.
{% endhint %}

## Example

```programlisting
^(?i)(SUMMER).*
```


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