> ## 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.


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