> ## Documentation Index
> Fetch the complete documentation index at: https://docs.usekinetic.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Variables & Hidden Fields

> Capture background data and perform calculations without visible form fields.

Found under **Settings → Variables & Hidden Fields** in the form builder.

## Hidden Fields

Hidden fields capture data invisibly and optionally sync it to Klaviyo profiles. They are not shown to the user but are included in the form submission data.

### Source Types

| Source            | Description                                 | Example                                |
| ----------------- | ------------------------------------------- | -------------------------------------- |
| **Klaviyo**       | Pull from the recipient's Klaviyo profile   | First name, city, custom properties    |
| **URL parameter** | Capture a value from the page URL           | `?utm_source=email` → captures `email` |
| **Static**        | A fixed value submitted with every response | Always submits `"campaign_2025"`       |

### Presets

Common Klaviyo profile fields are available as one-click presets:

* First Name, Last Name, Email, Phone Number, City, Country, Region

### Configuration Options

| Option                   | Description                                                                                                    |
| ------------------------ | -------------------------------------------------------------------------------------------------------------- |
| **Key**                  | The field name used in the submission data                                                                     |
| **Source type**          | Where the value comes from (Klaviyo, URL parameter, or static)                                                 |
| **Value**                | The source value — a Klaviyo Liquid variable, URL param name, or static string                                 |
| **Sync to profile**      | When enabled, pushes the value back to the Klaviyo profile on submission                                       |
| **Klaviyo property key** | Custom property name when syncing to Klaviyo (e.g. capture as `utm_source` but store as `acquisition_channel`) |
| **Prefix / Suffix**      | Prepend or append text to the captured value                                                                   |
| **Fallback**             | Default value if the source is empty                                                                           |

### Using Hidden Fields in the Form

Hidden field values can be used as merge tags inside the form itself. Use `{{hidden:key}}` in field labels, welcome headlines, or intro text to personalize the form with the captured value.

For example, if you have a hidden field with key `first_name` sourced from Klaviyo, you can write a welcome headline like:

> Hi `{{hidden:first_name}}`, we have a few questions for you!

The placeholder is replaced at runtime with the actual value. If the value is empty, the fallback is used (or the placeholder is removed).

<Tip>
  Hidden fields are useful for tracking attribution (UTM parameters), personalizing the form experience (e.g. greeting users by name), or enriching Klaviyo profiles with data from other sources.
</Tip>

## Variables

Variables are numeric values that can be used for scoring and calculations across form pages. They work together with the [Logic Builder](/form-builder/logic) to create scored quizzes and assessments.

| Option            | Description                      |
| ----------------- | -------------------------------- |
| **Name**          | The variable name (e.g. `score`) |
| **Initial value** | The starting value (default: 0)  |

Variables are manipulated by the Logic Builder's Scoring and Branching tabs — answer options can add, subtract, or set variable values. The final variable value can determine which end screen is shown.