> For the complete documentation index, see [llms.txt](https://developer.harness.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://developer.harness.io/resilience-testing/chaos-engineering/chaos-experiments/fault-template.md).

# Runtime variable support in experiments

Runtime variables provide flexibility in chaos experiments by allowing you to customize experiment parameters at execution time rather than hardcoding them during creation.

{% hint style="info" %}
**NEW CHAOS STUDIO FEATURE**

**Runtime input variables** are part of the enhanced **New Chaos Studio** experience. If you're an existing customer and want access to new features, contact your Harness support representative. For more details, see [New Chaos Studio Features](/resilience-testing/chaos-engineering/readme.md#new-chaos-studio-features).
{% endhint %}

### Create and Run Experiments <a href="#create-and-run-experiments" id="create-and-run-experiments"></a>

You can execute chaos experiments using either static values or dynamic runtime values.

* **Static variables**: Define them directly in the experiment and use them without any modification.
* **Runtime variables**: Specify them using `<+input>`, allowing customization at [runtime](#use-runtime-variables) or through [saved input sets](#use-pre-defined-input-sets).

#### Use Runtime Variables <a href="#use-runtime-variables" id="use-runtime-variables"></a>

To set up an experiment, specify details such as the name, environment, infrastructure, and fault name. In the **Target Application** and **Tune Fault** modals, you can choose between **Fixed value** and **Runtime Input**. Once you choose the input type, **Save** the changes.

![runtime variables](/files/EaKprLhKz6e7ziImKomq)

![runtime variables](/files/AEhvT4un6kdfVZDLPS4c)

{% hint style="info" %}

* If you don't provide values for certain fields (which are not mandatory), the experiment executes with default values.
* Variables specified as runtime inputs appear as editable fields in the UI, whereas static fields appear as display-only.
  {% endhint %}

#### Use Runtime Inputs in Pipelines <a href="#use-runtime-inputs-in-pipelines" id="use-runtime-inputs-in-pipelines"></a>

When you add a chaos experiment with runtime inputs to a Harness CD pipeline, those inputs automatically appear in the **Experiment Inputs** section of the chaos step configuration. You can then configure each input to be a runtime input for the pipeline as well, allowing you to provide values when the pipeline runs.

This enables you to:

* Reuse the same experiment across multiple pipelines with different configurations
* Dynamically provide experiment parameters at pipeline execution time
* Customize chaos validation based on deployment context

For more information on using chaos experiments with runtime inputs in CD pipelines, see [Using Runtime Inputs in Chaos Experiments](/resilience-testing/chaos-engineering/integrations/cicd/harness-cd.md#using-runtime-inputs-in-chaos-experiments).