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

# Use Hidden Fields for Tracking Data

> Use hidden fields to capture tracking data like UTM parameters and affiliate IDs without displaying them to users.

Hidden Fields allow you to capture and store extra data about your visitors without displaying anything on the page. This data is automatically saved with the lead when the form or quiz is submitted.

They are mainly used for tracking and attribution, helping you understand where your leads are coming from.

<video src="https://mintcdn.com/landerlab-babdc23f/TdcM2TWHYqUYlTLv/videos/Hidden-Fields.webm?fit=max&auto=format&n=TdcM2TWHYqUYlTLv&q=85&s=bcc8eeac3f5230a3174ba65c8d1c636c" controls={true} data-path="videos/Hidden-Fields.webm" />

## How to Add a Hidden Field

Open your landing page and click **Edit Quiz** to enter the builder.

Click **Add Block** and select **Hidden Field**.

Once added, click on the block to configure it.

Set the **Name** of the field. This should match the parameter you want to capture, such as `utm_source` or `aff_id`.

Leave the **Default Value empty** if you plan to pass values dynamically through the URL.

Click **Update**, then exit the builder and **Publish or Republish** your landing page.

## How Hidden Fields Work

Hidden Fields automatically capture values from URL parameters.

For example, if your page URL contains:

`?utm_source=facebook`

And your Hidden Field is named:

`utm_source`

Then the value **facebook** will be captured and stored with the lead.

The parameter name in the URL must match the field name (it is not case-sensitive)

***

## Common Use Cases

**Affiliate Tracking**\
You can track which partner or affiliate generated a lead.

Create a Hidden Field named `aff_id`, and use links like:\
`?aff_id=12345`

When a user lands on the page, the value is captured and stored with the lead.

**UTM Tracking**\
You can capture campaign and traffic data using standard UTM parameters:

* `utm_source` (e.g., Facebook, Google)
* `utm_medium` (e.g., CPC, email)
* `utm_campaign` (campaign name)

For example:\
`?utm_source=google&utm_medium=cpc&utm_campaign=summer_sale`

Each value will automatically be saved in the corresponding Hidden Field.

## Important Notes

The field name must match the URL parameter exactly.

Hidden Fields are not visible to users at any point.

All captured values are automatically sent along with the lead data.

If you want dynamic tracking, always leave the Default Value empty.