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Using WebGL Templates

When you build a WebGL project, Unity embeds the player in an HTML page so that it can be played in the browser. The default page is a simple white page with a loading bar on a grey canvas. Alternatively, you can select a minimal template (with only the necessary boilerplate code to run the WebGL content) in the Player settings (menu: Edit > Project Settings, then select the Player category).

The built-in HTML pages are fine for testing and demonstrating a minimal Player, but for production purposes, it is often good to see the Player hosted in the page where it will eventually be deployed. For example, if the Unity content interacts with other elements in the page via the external call interface then it must be tested with a page that provides those interacting elements. Unity allows you to supply your own pages to host the Player by using WebGL templates.

Structure of a WebGL Template

Custom templates are added to a project by creating a folder called “WebGLTemplates” in the AssetsAny media or data that can be used in your game or Project. An asset may come from a file created outside of Unity, such as a 3D model, an audio file or an image. You can also create some asset types in Unity, such as an Animator Controller, an Audio Mixer or a Render Texture. More info
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folder - the templates themselves are sub-folders within this folder. Each template folder contains an index.html file along with any other resources the page needs, such as images or stylesheets.

Once created, the template appears among the options on the Player settings. The name of the template is the same as its folder. Optionally, the folder can contain a file named thumbnail.png, which should have dimensions of 128x128 pixelsThe smallest unit in a computer image. Pixel size depends on your screen resolution. Pixel lighting is calculated at every screen pixel. More info
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. The thumbnail image is displayed in the inspectorA Unity window that displays information about the currently selected GameObject, Asset or Project Settings, alowing you to inspect and edit the values. More info
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to hint at what the finished page will look like.

The html file needs to contain at least the following elements:

  • Script tag for the Unity WebGLA JavaScript API that renders 2D and 3D graphics in a web browser. The Unity WebGL build option allows Unity to publish content as JavaScript programs which use HTML5 technologies and the WebGL rendering API to run Unity content in a web browser. More info
    See in Glossary
    loader: <script src="%UNITY_WEBGL_LOADER_URL%"></script>

  • Script for instantiating the game: <script> var gameInstance = UnityLoader.instantiate("gameContainer", "%UNITY_WEBGL_BUILD_URL%");</script>

  • A <div> tag, which id is used in the instantiation function. The contents of this div will be replaced with the game instance.

UnityLoader.instantiate(container, url, override)

UnityLoader.instantiate is responsible for creating a new instance of your content.

  • container can be either a DOM element (normally a <div> element) or an id of a DOM element. If the DOM element is provided, then the game will be instantiated immediately. If an id of a DOM element is provided, then the game will be instantiated after the whole document is parsed (which means you can provide an id of a DOM element which has not yet been created at the time of UnityLoader.instantiate() call).

  • url specifies the address of the json file, which contains information about the build (you may use the %UNITY_WEBGL_BUILD_URL% variable which will be automatically resolved at build time).

  • override is an optional parameter which can be used to override the default properties of the game instance. For example, you can override the compatibilityCheck, onProgress and popup functions, as those are properties of the game instance. Note that Module is a property of the game instance as well, so the properties of the Module can be overridden at instantiation time too. Consider the following example:

UnityLoader.instantiate("MyContainer", "%UNITY_WEBGL_BUILD_URL%", {
  compatibilityCheck: function (gameInstance, onsuccess, onerror) {
    if (!UnityLoader.SystemInfo.hasWebGL) {
      gameInstance.popup("Your browser does not support WebGL",
        [{text: "OK", callback: onerror}]);
    } else if ( {
      gameInstance.popup("Please note that Unity WebGL is not currently supported on mobiles. Press OK if you wish to continue anyway.",
        [{text: "OK", callback: onsuccess}]);
    } else if (["Edge", "Firefox", "Chrome", "Safari"].indexOf(UnityLoader.SystemInfo.browser) == -1) {
      gameInstance.popup("Please note that your browser is not currently supported for this Unity WebGL content. Press OK if you wish to continue anyway.",
        [{text: "OK", callback: onsuccess}]);
    } else {
  onProgress: MyProgressFunction,
  Module: {
    onRuntimeInitialized: MyInitializationCallbackFunction,

Template tags

During the build process, Unity looks for special tag strings in the page text and replaces them with values supplied by the Editor. These include the name, onscreen dimensions and other useful information about the player.

Tags are delimited by percent signs (%) in the page source. For example, if the product name is defined as MyPlayer in the Player settings:


…in the template’s index file will be replaced with


…in the host page generated for the build. The complete set of tags is given below:

  • UNITY_WEB_NAME: Name of the player.

  • UNITY_WEBGL_LOADER_URL: URL of the UnityLoader.js script, which performs instantiation of the build.

  • UNITY_WEBGL_BUILD_URL: URL of the JSON file, containing all the necessary information about the build.

  • UNITY_WIDTH and UNITY_HEIGHT: Onscreen width and height of the player in pixels.

  • UNITY_CUSTOM_SOME_TAG: If you add a tag to the index file in the form UNITY_CUSTOM_XXX, then this tag will appear in the Player settings when your template is selected. For example, if you add &lt;title&gt;Unity Player | %UNITY_CUSTOM_MYTAG%&lt;/title&gt; to the source, the Player settings look like this:

The textbox next to the tag’s name contains the text that the custom tag will be replaced with during the build.


To illustrate the use of the template tags, here is the HTML source that Unity uses for its minimal WebGL template.

<!DOCTYPE html>
<html lang="en-us">

    <meta charset="utf-8">
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <title>Unity WebGL Player | %UNITY_WEB_NAME%</title>
    <script src="%UNITY_WEBGL_LOADER_URL%"></script>
    var gameInstance = UnityLoader.instantiate("gameContainer", "%UNITY_WEBGL_BUILD_URL%");
    <div id="gameContainer" style="width: %UNITY_WIDTH%px; height: %UNITY_HEIGHT%px; margin: auto"></div>

Both minimal and default templates can be found in the Unity installation folder under Editor\Data\PlaybackEngines\WebGLSupport\BuildTools\WebGLTemplates on Windows or /PlaybackEngines/WebGLSupport/BuildTools/WebGLTemplates on Mac.

Adding a progress bar

Unity WebGL content will automatically render a default progress bar for you when it loads. You can override the default loading bar by providing your own progress function as an additional instantiation parameter. For example:

var gameInstance = UnityLoader.instantiate("gameContainer", "%UNITY_WEBGL_BUILD_URL%", {onProgress: UnityProgress});

where UnityProgress is a function of 2 arguments: gameInstance (identifies the game instance the progressbar belongs to) and progress (a value from 0.0 to 1.0, providing information about the current loading progress).

For example, the progress function in the default WebGL template looks the following way:

var gameInstance = UnityLoader.instantiate("gameContainer", "%UNITY_WEBGL_BUILD_URL%", {onProgress: UnityProgress});

For example, the progress function in the default WebGL template looks the following way:

function UnityProgress(gameInstance, progress) {
  if (!gameInstance.Module)
  if (!gameInstance.logo) {
    gameInstance.logo = document.createElement("div");
    gameInstance.logo.className = "logo " + gameInstance.Module.splashScreenStyle;
  if (!gameInstance.progress) {    
    gameInstance.progress = document.createElement("div");
    gameInstance.progress.className = "progress " + gameInstance.Module.splashScreenStyle;
    gameInstance.progress.empty = document.createElement("div");
    gameInstance.progress.empty.className = "empty";
    gameInstance.progress.full = document.createElement("div");
    gameInstance.progress.full.className = "full";
  } = (100 * progress) + "%"; = (100 * (1 - progress)) + "%";
  if (progress == 1) = = "none";

You can use it as is or as reference for your own templates. Since the progress bar is completely implemented in JavaScript, you can customize or replace it to show anything you want as a progress indication.