> For the complete documentation index, see [llms.txt](https://docs.anedot.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.anedot.com/action-pages/page-builder/hidden-fields.md).

# Hidden Fields

Use hidden fields to save tracking values with each Action Page submission. Set a default value, a page-specific value, or pass a value in the link.

A **hidden field** saves a value with each submission without showing anything to the donor. Use it to track a source or campaign, or to send a value to your integrations. Hidden fields are a type of custom field, added in the Page Builder under **Page > Form**. This article covers adding a hidden field and where its value comes from.

## Add a Hidden Field

To add a hidden field:

1. Go to **Action Pages > Pages**.
2. Hover over the page you want to edit.
3. Click **⋮ > Edit**.
4. Select **Page > Form**.
5. Under **Custom fields**, click **New** and choose the Hidden type, or click **Existing** to add a hidden field your account already has.
6. (Optional) Enter a **Default value**.
7. (Optional) Enter a **Page-specific value** to use a different value on this page only.
8. Click **Save**.

Each new submission from the page saves the hidden value.

## Where the Value Comes From

When a donor opens the page, the hidden field uses the first value it finds, in this order:

1. A value in the page link, using the field's internal name as a URL parameter.
2. The **Page-specific value** for this page.
3. The **Default value**.

Example: Your hidden field has the internal name source, a Default value of "website" and a Page-specific value of "spring-appeal." A donor who opens the link with `?source=email` saves "email." A donor who opens the plain link saves "spring-appeal."

## Internal Names

Anedot creates each custom field's internal name from its label, in lowercase with underscores. The internal name is what you use in links and what your integrations receive. Changing the label later doesn't change the internal name.

## Related Articles

* [Custom Form Fields](/action-pages/page-builder/custom-form-fields.md)
* [URL Parameters](/action-pages/advanced-features/url-parameter.md)
* [Page Builder Overview](/action-pages/page-builder.md)


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation by asking a question.

Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters:

```
GET https://docs.anedot.com/action-pages/page-builder/hidden-fields.md?ask=<question>&goal=<user_goal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.