> For the complete documentation index, see [llms.txt](https://docs.hackle.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.hackle.io/en/ab-test/create-and-configure/abtest-parameter.md).

# Parameter Settings

### What are Parameter Settings?

* You can implement the changes for each A/B Test variation as parameters.
* Apply values such as text, URLs, and numbers flexibly. Complex values can be managed as JSON.
* Parameter values can be changed in the Dashboard. Changed values are applied to your service right away.

{% hint style="warning" %}
Before you configure

* When you can configure and edit: Only while the A/B Test in the Production Environment is in **Draft** status.
* Changing after the test starts: You need to create a new test version or a new A/B Test.
* Environment: You can configure the Production Environment and the Development Environment separately.
* Maximum count: You can add up to 10 parameters per A/B Test.

**Parameters cannot be modified after the A/B Test starts in the Production Environment.**
{% endhint %}

### Configure Parameters

![Parameter settings screen](https://143363954-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FyAVlNQhS253reum0Ce94%2Fuploads%2Fgit-blob-e95ad2db3fe648ece58c6060c67d49865f3525c0%2F6b1387b-parameter_setting_kr_7d323200325d501a.png?alt=media)

<table><thead><tr><th width="152.1875">Item</th><th width="267.59765625">Description</th><th>Constraints</th></tr></thead><tbody><tr><td><strong>Parameter Key</strong></td><td>Enter the parameter key used in your code.</td><td><p>Only letters, numbers, <code>_</code>, <code>-</code>, and <code>.</code> can be used. Must be 1–128 characters.</p><p>Cannot be duplicated within the same A/B Test.</p></td></tr><tr><td><strong>Parameter Type</strong></td><td>Select the format of the parameter value.</td><td>Supports <code>String</code>, <code>Number</code>, <code>Boolean</code>, and <code>JSON</code>. The values you can enter differ by type.</td></tr><tr><td><strong>Parameter Value</strong></td><td>Enter the value to apply to each variation.</td><td>Not applied to users until the test starts.</td></tr><tr><td><strong>Add Parameter</strong></td><td>Add a new parameter setting.</td><td>You can add up to 10.</td></tr></tbody></table>

### How to Apply

1. On the A/B Test detail page, create a parameter key for the item you want to manage.
2. Select the parameter type that matches the value.
3. Enter the parameter value to apply to each variation.
4. Apply the parameter key in the code for each variation.
5. After deploying, verify on a test device that the key and value are delivered correctly.
6. Once you have confirmed it works, start the A/B Test.


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