> For the complete documentation index, see [llms.txt](https://docs.feathery.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.feathery.io/platform/build-forms/elements/custom-html-js-css-and-iframes.md).

# Custom HTML, JS, CSS, and Iframes

You can add custom HTML, Javascript, and iframes directly to your Feathery form.

## Custom Components

You can add custom HTML components, Javascript, and iframes directly to your form. After selecting a [container](/platform/build-forms/elements/basic/container.md), you can configure its iframe URL or add custom code to embed. Both iframe URLs and custom code support dynamic values via [double-curly brace field syntax](/platform/build-forms/logic/display-dynamic-text.md).

To add custom CSS to specific elements, you can query them by their IDs and apply custom CSS to the retrieved elements.

<figure><img src="https://640450274-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FHAVngDAEk3s8Bw7P6Ntz%2Fuploads%2FWW7ATVPYOqVMUVS7yDrn%2FScreenshot%202023-05-05%20at%205.07.26%20PM.png?alt=media&amp;token=b398461f-e78a-483e-a6f0-4b74d4e31282" alt="" width="358"><figcaption></figcaption></figure>

## Form Head Code

If you want to add HTML or JS header code to your form, you can do so in your form settings under the **Form Properties** tab.

<figure><img src="https://640450274-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FHAVngDAEk3s8Bw7P6Ntz%2Fuploads%2FC7l9hJJ1RwR82HgHOVqv%2FScreenshot%202025-01-23%20at%201.17.36%E2%80%AFAM.png?alt=media&amp;token=7506925c-d143-4590-874d-ff4e70305a9d" alt="" width="375"><figcaption></figcaption></figure>

## Form CSS

To apply CSS classes to your overall form, you can add the CSS within the **Form Properties** tab.

<figure><img src="https://640450274-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FHAVngDAEk3s8Bw7P6Ntz%2Fuploads%2FrSXxFRNZBCOABHG1B4TQ%2FScreenshot%202025-01-23%20at%201.19.31%E2%80%AFAM.png?alt=media&amp;token=bf458a1d-b226-456e-90c7-1a9228e69d6d" alt="" width="375"><figcaption></figcaption></figure>

## JSX Components

If you want to [add JSX components](/develop/react/api-guide/form/custom-jsx-components.md) to your embedded React form, you can do so from our [React SDK](https://docs.feathery.io/develop/react/api-guide/form/custom-jsx-components).


---

# 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.feathery.io/platform/build-forms/elements/custom-html-js-css-and-iframes.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.