---
title: "HTML FAQs"
description: "How do I include the iFrame Client in my HTML file?"
permalink: /docs/runtime/all-ui-components/html/html-faqs/
---
# HTML FAQs

<a id="how-do-i-include-the-journeyapps-iframe-client-in-my-html-file"></a>

#### How do I include the [iFrame Client](https://github.com/journeyapps/journey-iframe-client) in my HTML file?

Please see [this section](/docs/runtime/all-ui-components/html/html-advanced-topics/#include-the-journeyapps-iframe-client).

#### **Are there any limitations to what kind of websites I can reference as a** [**remote HTML source**](/docs/runtime/all-ui-components/html/#types-of-html-sources)**?**

Yes - sources may have restrictions that prevent them from loading in external iFrames. A common example is when cross origin is not supported, as in the case of:

```xml
<html src="http://www.google.com" />
```

#### What kind of data can I include in the [`post()`](/docs/runtime/all-ui-components/html/#post) method?

You'll be able to include values such as number or strings, or serialized objects.

Posting a complex object (e.g. objects that include promises) or a function will likely throw an error. For such objects you might need to Base64 encode and/or apply `JSON.stringify()` before passing it in the `post()`. You will only be able to post function references, not functions themselves.

#### Can I use the developer console to troubleshooting the iFrame Client?

Yes, by selecting it from the list of available contexts:

<div align="center">![](./media/spaces-2f9tchlr67elhbojpvhhud-2fuploads-2ffuaes9h5mxmo5ujojitw-2fscreen-20shot-202022-08-26-20at-208.27.42-20am-cb01ca10.png)</div>

#### Why am I receiving sandboxing errors?

If your HTML content is not loading and you are seeing references to sandboxing issues in the developer console, you are most likely trying to display [restricted content](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/iframe#attr-sandbox).

The iFrame Client currently allows the following:

* `allow-same-origin`
* `allow-scripts`
* `allow-forms`
* `allow-modals`

Any other content will result in a sandboxing error.

Note that no additional restrictions are added/lifted on remote HTML sources by the Runtime. The source may have its own sandboxing restrictions.

#### I am getting a "Callback for ... is already registered" error when returning to a view that has an HTML component on it. Why?

On Runtime 4.86.4 and later, `.on()` replaces the previous callback for the same command on that component and view. Check the running Runtime version if you see this error.

On older versions, register the callback once for that view instance, or remove the view from the stack before opening a new instance. See the [HTML callback reference](/docs/runtime/all-ui-components/html/#on).

#### Why am I am getting a "No HTML component matching id: ... found" error upon entering my view?

You will receive this error when you attempt to `post()` to your iFrame Client before it has loaded successfully. For this you can add a [`DOMContentLoaded`](https://developer.mozilla.org/en-US/docs/Web/API/Window/DOMContentLoaded_event) or `window.addEventListener('load')` event to the iFrame, and post a message back to the app. An example of this is included [here](/docs/runtime/all-ui-components/html/guide-html-and-journeyapps-iframe-client/#basic-example).