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# Preview the Output of a Transformation

> For the full documentation index, see: https://docs.mulesoft.com/llms.txt

You can provide sample input data to your Transform Message component to see how the transformation
affects it. You don’t need to deploy your project to use this feature. A sample output is updated in
real time as you make changes both to the sample input and the transformation.

1.  Click on the root of the input pane and select **Edit Sample Data**.

    ![A dropdown menu with options to set metadata, clear metadata, edit sample data, and configure the reader](/mulesoft/current/en-us/studio/_images/dataweave-edit-sample-data.png)

    A new tab opens with an empty scaffolding of your input structure. Values are populated with the
    string `????` as a placeholder.

    > [!NOTE] When the input is of type POJO, samples must be written in DataWeave format. This is
    > not a transformation in itself, just a way to express how data is structured.

2.  Replace placeholder values with sample values to see how they are mapped out to the preview
    pane.

    ![A code editor displaying a JSON file with fields for item amount, payment, product, salesperson, and shop](/mulesoft/current/en-us/studio/_images/dw-populate-sample-data.png)

    > [!TIP] To reset the sample to the original scaffolding with placeholders, click the
    > **rescaffold button**
    > ![A menu icon with three horizontal lines and a right arrow](/mulesoft/current/en-us/studio/_images/dw-rescaffold-button.png).
    > Note that any sample data you provided is lost.

3.  Enable the preview pane by clicking on the **Preview** button on the top-right of the editor.

    As you make changes in the DataWeave code or your sample data, notice how the output data
    structure changes.

    > [!NOTE] If your transformer has multiple outputs (for example, to both the payload and a
    > variable), the **Preview** pane displays the one corresponding to the currently selected
    > transformation.

4.  Test your transformation for any special characters or structures that might arrive, verify that
    the output is what you expected.

    > [!NOTE] Note that samples defined in this pane work only within the **Transform Message**
    > component, they don’t alter the metadata that’s propagated to other components in the flow,
    > and their values aren’t propagated onwards. They aren’t used in your running application as
    > default values nor in any other way.

## See Also

- [Workflow: Create a Mapping](https://docs.mulesoft.com/studio/workflow-create-mapping-ui-studio)

- [Transform Message Component](https://docs.mulesoft.com/studio/transform-message-component-concept-studio)

- [DataWeave Language](https://docs.mulesoft.com/mule-runtime/latest/dataweave)