Customizing the Player Web Page

How to customize the web page that plays back streamed video and audio, and how to exchange events between the page and the UE4 application.

Google has informed developers of a vulnerability in versions (earlier than M102) of WebRTC. Impacts, workarounds, and updates can be found here.

However, with a little creativity and some knowledge of web technologies like JavaScript and HTML, you can take full control over the player page, creating your own custom UIs for interacting with your Unreal Engine content remotely. You can trigger and respond to gameplay events, issue console commands to control the Unreal Engine's behavior, and more.

We recommend using the default player page as a starting point for creating your own custom player page. You'll find this page at Samples/PixelStreaming/WebServers/SignallingWebServer/www/player.html under your Unreal Engine installation folder. Then, use the information on this page to learn how to extend your page and tie it in with your Project's gameplay logic.

Default player page

Customized player with HTML5 UI

HTML Page Requirements

Your custom HTML player page must follow a few minimal requirements.

  • You must include the /scripts/webRtcPlayer.js file. This file handles communication between the browser and the Unreal Engine application, receiving and showing the media stream from the server. Do not modify this JavaScript file unless absolutely necessary.

    <script type="text/javascript" src="scripts/webRtcPlayer.js"></script>
  • We highly recommend that you also include the /scripts/app.js file as well. This file sets up event listeners that process the keyboard, mouse, and touch events. It also contains several functions and hooks that you can take advantage of in your player page, described in the sections below on this page. If you have some knowledge of JavaScript, you should feel free to dig into the code of this file and modify the default behavior to suit your needs. For example, if you want to disable keyboard inputs but leave mouse and touch events working, you will need to customize this file by finding and commenting out the code that handles keyboard events.

    <script type="text/javascript" src="scripts/app.js"></script>
  • The page must have a div element with the ID player. This element is replaced with the video frames streamed from the UE4 application.

    <div id="player"></div>
  • You must call the load function provided by the app.js file when your page loads. For example, you can do this by adding an onload handler to the body tag:

    <body onload="load()">

Player File Location and URL

You have a few options for where you can place your custom HTML player page, and how client browsers can access it.

  • You can make a folder called custom_html inside the root folder of your Signaling and Web Server, and place your custom HTML player page inside this folder. It will then be accessible by appending its filename to the IP address or hostname of the computer running the Signaling and Web Server.
    For example, a file named custom_html/myplayerpage.html would be accessible at

  • You can customize the HomepageFile parameter for the Signaling and Web Server, and set the path to the filename of your custom HTML player page relative to the root folder of the Signaling and Web Server. It will then be accessible when you access the IP address or hostname of the computer running the Signaling and Web Server.
    For example, if you save a file to Engine/Source/Programs/PixelStreaming/WebServers/SignallingWebServer/myfolder/myplayerpage.html, and you set the HomepageFile parameter to myfolder/myplayerpage.html, the page would be accessible without needing to provide a file name in the URL:

  • You can also use the AdditionalRoutes parameter for the Signaling and Web Server to customize the mapping between URL paths and local folders on your computer.

For additional details on these parameters, see also the Pixel Streaming Reference.

Customizing Player Input Options

The app.js file offers some JavaScript configuration parameters that you can override in your custom player page to control the way the player widget responds to user interactions. The inputOptions object exposes the following properties:






Determines whether or not the player widget captures and locks the mouse when the player interacts with the widget. Accepts the following values:

  • ControlSchemeType.LockedMouse - When this control scheme is active, clicking on the player widget causes it to capture and lock the mouse cursor. Any further movements of the mouse are passed immediately to the input controller in the Unreal Engine application. This typically allows the user to move and rotate the camera by simply dragging the mouse. To release the cursor from the control of the player widget, the user can press the Esc key.

  • ControlSchemeType.HoveringMouse - When this control scheme is active, the mouse cursor hovers over the player widget without interacting with it. In order to send the mouse movements to the input controller of the Unreal Engine application, the user needs to click and hold the left button of the mouse.



When this setting is enabled, the player widget will intercept function keys (F1 to F12) and the Tab key, and pass those keypress events through to the Unreal Engine application rather than allowing the browser to process them normally. This means, for example, that while this setting is active, pressing F5 will not refresh the player page in the browser. Instead, that event is passed through to the Unreal Engine application, and has its usual function of switching the view to visualize shader complexity.



When this option is enabled, and the user is viewing the stream on a device with a touch screen such as a smartphone or tablet, this setting causes single-finger touch events to be interpreted by the Unreal Engine application as mouse clicks and drag events. Enabling this setting can provide users on mobile devices with the ability to partially control your Unreal Engine application, even when the application's input controller does not specifically handle touch input events.

You can set these values in your player page by including a code block like the following. Make sure that you run this code any time after you load the app.js file into the page, but before you call its load function.

inputOptions.controlScheme = ControlSchemeType.HoveringMouse;
inputOptions.fakeMouseWithTouches = true; 

Disabling User Input

To disable user input entirely for one or more types of input device, you can override the following functions in the JavaScript environment for your player page with empty implementations:

  • registerHoveringMouseEvents - Disables all input mouse events when the inputOptions.controlScheme is set to ControlSchemeType.HoveringMouse.

  • registerLockedMouseEvents - Disables all input mouse events when the inputOptions.controlScheme is set to ControlSchemeType.LockedMouse.

  • registerTouchEvents - Disables touch events on mobile devices and tablets.

  • registerKeyboardEvents - Disables all keyboard events.

For example, you could include this block of JavaScript in your player HTML page to disable all inputs. As above, run this code any time after you load the app.js file into the page, but before you call its load function.

registerHoveringMouseEvents = function() {}
registerLockedMouseEvents = function() {}
registerTouchEvents = function() {}
registerKeyboardEvents = function() {} 

To keep one or more types of inputs active, comment out or remove the line that corresponds to the type of input you want to keep.

Customizing the Player Widget Style

In your custom HTML player page, you should have defined the Pixel Streaming player widget: a div element with id="player". You can use standard HTML and CSS methods to add styling to this widget.

However, the widget may occasionally need to reinitialize its size. This typically occurs when the browser window is resized (if the widget is set to automatically fill the available space), or when the resolution of the input video stream is updated. When this happens, the style attribute of the player element is overwritten with new values, which can potentially overwrite values that you have set in your own HTML or JavaScript.

To avoid this, you can set your custom CSS values in a special global variable named styleAdditional. Whenever app.js needs to resize the player and clear its style, it will append the values you set in the styleAdditional variable to the end of the new style attributes it assigns to the player element. For example, the following value changes the mouse cursor to a hand when the user hovers the mouse over the player widget:

styleAdditional = 'cursor: grab; cursor: -moz-grab; cursor: -webkit-grab';

Timing Out Inactive Connections

In some kinds of Pixel Streaming deployments, you may want to automatically disconnect users who have been inactive for a certain period of time. For example, if you have a limited pool of Unreal Engine applications available, with access to those instances controlled by a matchmaking server, you may need to drop inactive older connections in order to make sure that you have application instances available to handle new incoming connection requests.

You can configure your Pixel Streaming player page to detect when a user appears to be away from keyboard (AFK)—that is, when the user has not interacted with the player widget within a customizable time interval. The AFK system warns the user:

AFK timeout warning

If the user continues not to respond, the AFK system ultimately disconnects their session.

Any user interaction with the player panel resets the AFK timer. This includes mouse moves and drags, mouse button presses, keyboard presses, touch events on mobile devices, and custom interactions you set up with the emitCommand and emitUIInteraction functions.

To use the AFK system, set the following three properties in the JavaScript of your player page. Do this after you load the app.js file, but before you call its load function.




Determines whether the AFK system should check for user interactions. The default is false; set this value to true to time out inactive connections.


Sets the maximum time interval, in seconds, that the user can remain away from keyboard before seeing a warning overlay in the player widget. The default is 120, or two minutes.


After the afk.warnTimeout interval has elapsed and the user sees a warning message about being disconnected, this variable sets the time interval, in seconds, before the user's connection is automatically disconnected unless they interact with the player widget. The default is 10.

If you want to customize the content of the overlay, you can redefine the updateAfkOverlayText() function in your player page. In your implementation, set the afk.overlay.innerHTML property to the HTML that you want the player widget to display when users have been away longer than the AFK timeout value.

This page was written for a previous version of Unreal Engine and has not been updated for the current Unreal Engine 5.0 release.
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