Version: 2021.3
Building and distributing a WebGL project
Reduce load times with AssetBundles

Building your WebGL application

To create a build for WebGL, go to File > Build Settings from Unity’s main menu. In the Platform list, select WebGL and then click Switch Platform.

When you have configured the Build Settings, choose from the following two options:

  • Build builds your application into a Player.
  • Build and Run builds your application in a Player, and opens that Player on your target platform.
Build Settings Window
Build Settings Window

The Unity build system for 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
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supports the following settings:

Setting Function
Texture CompressionA method of storing data that reduces the amount of storage space it requires. See Texture Compression, Animation Compression, Audio Compression, Build Compression.
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Select from the available formatting options below to set the default texture compression3D Graphics hardware requires Textures to be compressed in specialized formats which are optimized for fast Texture sampling. More info
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format for the textures in the project.You can also use this setting to change from a script or using the command-line switch -setDefaultPlatformTextureFormat. For more information, see the texture compression format overview.This setting is also available in the Player settingsSettings that let you set various player-specific options for the final game built by Unity. More info
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window.
Use default format (DXT) This is the default compression format.
ETC This extension is part of the WebGL API and exposes the ETC compressed texture formatA file format for handling textures during real-time rendering by 3D graphics hardware, such as a graphics card or mobile device. More info
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.
ETC2 This extension is part of the WebGL API and exposes the ETC compressed texture format. Use this texture compression format if using OpenGL 4.3.
ASTC This texture compression format is a popular choice due its wide range of derived compression ratios. For instance, ASTC compression is available for most Intel GPUs and Nvidia Tegra chips.
DXT This extension supports the DXTn/BCn compression format.
Development BuildA development build includes debug symbols and enables the Profiler. More info
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Enable this setting to include scripting debug symbols and the Profiler in your build. When you enable this, Unity sets the DEVELOPMENT_BUILD scripting define. You should use this setting only when you want to test your application. Note that development builds do not minify content, which means the development builds are very large to distribute.
Code Optimization Select the optimization mode to use for compiling the WebGL code.
Speed This is the default setting. Selecting this generates WebGL code that is optimized for runtime performance.
Size Selecting this generates WebGL code that is optimized for build size. This is particularly useful when building WebGL games to run on mobile browsers on Android and iOSApple’s mobile operating system. More info
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, where the default optimize-for-speed option would generate larger WebAssembly files for mobile devices to consume.
Autoconnect Profiler Typically, when enabled, this setting allows you to automatically connect the Unity Profiler to your build. However, for WebGL, as you cannot connect the ProfilerA window that helps you to optimize your game. It shows how much time is spent in the various areas of your game. For example, it can report the percentage of time spent rendering, animating, or in your game logic. More info
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to a running build, use this option to connect the content to the Editor instead. This is because the Profiler connection is handled using WebSockets on WebGL, but a web browser only allows outgoing connections from the content. For this setting to be available, you should enable the Development Build option.
Deep Profiling Support Enable this setting to turn on Deep Profiling in the Profiler. This makes the Profiler instrument every function call in your application and returns more detailed profiling data. When you enable Deep Profiling Support, it might slow down script execution. This option is only available if you enable the Development Build option.
IL2CPP Code Generation Define how Unity manages IL2CPP code generation. This option is only available if you are using IL2CPP for your scripting backend, not Mono. To change your scripting backend, go to Player Settings > Configuration > Scripting Backend and change from Mono to IL2CPP.
Faster runtime Generates code that is optimized for runtime performance. This is the default behavior in previous versions of Unity.
Faster (smaller) builds Generates code that is optimized for build size and iteration. It generates less code and produces a smaller build, but may have an impact on runtime performance, especially for generic code. You might want to use this option when faster build times are important, such as when iterating on changes
Build Use it build your application.
Build And Run Use it to view the WebGL Player locally. Unity uses a local web server to host your build, and opens it from a localhost URL. Alternatively, you can use a custom local web server with properly configured response headers. For more information, see WebGL: Compressed builds and server configuration.

For changing the settings for Asset Import Overrides, see Build Settings.

Build Folder

The Build folder contains the following files ([ExampleBuild] represents the name of the target build folder).

File name Contains
[ExampleBuild].loader.js The JavaScript code that the web page needs in order to load the Unity content.
[ExampleBuild].framework.js JavaScript runtime and plugins.
[ExampleBuild].wasm WebAssembly binary.
[ExampleBuild].mem A binary image to initialize the heap memory for your Player. Unity only generates this file for multi-threaded WebAssembly builds.
[ExampleBuild].data Asset data and ScenesA Scene contains the environments and menus of your game. Think of each unique Scene file as a unique level. In each Scene, you place your environments, obstacles, and decorations, essentially designing and building your game in pieces. More info
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.
[ExampleBuild].symbols.json Debug symbol names necessary to demangle an error stack trace. This file is only generated for Release builds when you enable the Debug Symbols option (File > Build Settings > Player Settings.)
[ExampleBuild].jpg A background image, which displays while the build is loading. This file is only generated when a Background Image is provided in the Player Settings (File > Build Settings > Player Settings > Splash Image). See the Splash Screen page for further information.

If you enable a Compression Method for your build, Unity identifies the extension that corresponds with the compression method and adds this extension to the names of the files inside the Build subfolder. If you enable Decompression Fallback, Unity appends the extension .unityweb to the build file names. Otherwise, Unity appends the extension .gz for the Gzip compression method, or .br for the Brotli compression method. For more information, see WebGL: Compressed builds and server configuration.

If you enable Name Files As Hashes in the Player Settings, Unity uses the hash of the file content instead of the default filename. This applies to each file in the build folder. This option allows you to upload updated versions of the game builds into the same folder on the server, and only upload the files which have changed between build iterations.

Note: Opening a Player directly from the file system might not work in some browsers. This is due to security restrictions applied to local file URLs.

Deep Profiling Support

Enable the Deep Profiling Support setting to make the Unity Profiler profile every function call in your application. For more information see the documentation on Deep Profiling.

Player settings

WebGL has some additional options in the Player settings (menu: Edit > Project SettingsA broad collection of settings which allow you to configure how Physics, Audio, Networking, Graphics, Input and many other areas of your project behave. More info
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, then select the Player category).

Other Settings

Strip Engine Code

Open Other Settings to access the Strip Engine Code option. This option is checked by default to enable code stripping for WebGL. With this option checked, Unity does not include code for any classes you don’t use. For example, if you don’t use any physics components or functions, the whole physics engineA system that simulates aspects of physical systems so that objects can accelerate correctly and be affected by collisions, gravity and other forces. More info
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is removed from your build. See the Stripping section below for more details.

Publishing Settings

Enable Exceptions

Open Publishing Settings to access Enable Exceptions. Enable Exceptions allows you to specify how unexpected code behavior (generally considered errors) is handled at run time. It has these options:

  • None: Select this if you don’t need any exception support. This gives the best performance and smallest builds. With this option, any exception thrown causes your content to stop with an error in that setting.
  • Explicitly Thrown Exceptions Only (default): Select this to capture exceptions which are explicitly specified from a throw statement in your scriptsA piece of code that allows you to create your own Components, trigger game events, modify Component properties over time and respond to user input in any way you like. More info
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    and to also ensure finally blocks are called. Note that selecting this option makes the generated JavaScript code from your scripts longer and slower; This might only be an issue if scripts are the main bottleneck in your project.
  • Full Without Stacktrace: Select this option to capture:
    • Exceptions which are explicitly specified from throw statements in your scripts (the same as in the Explicitly Thrown Exceptions Only option)
    • Null References
    • Out of Bounds Array accesses
  • Full With Stacktrace: This option is similar to the option above but it also captures Stack traces. Unity generates these exceptions by embedding checks for them in the code, so this option decreases performance and increases browser memory usage. Only use this for debugging, and always test in a 64-bit browser.

Select Publishing Settings to access Data Caching.

Data Caching

To access Data Caching, go to Publishing Setings via File > Build Settings > Player Settings > WebGL. This enables the browser to cache the main data files into the IndexedDB database.

Using the default browser HTTP cache does not guarantee that the browser caches a particular response. This is because the browser HTTP cache has limited space, and the browser might not be able to cache files that are too large.

To improve your loading speed, IndexedDB allows you to cache files above the browser limit. When you cache more files, you increase the chance that downloaded content is available on the user’s machine during the next run of the build.

Data Caching only caches the .data files in the IndexedDB cache for HTTP responses. To cache AssetBundles, you need to enable Data Caching and override unityInstance.Module.cacheControl(). To do this, make sure Module.cacheControl(url) returns must-revalidate for the requested AssetBundle URL. For example, you can override the unityInstance.Module.cacheControl() function in the fulfillment callback of the Promise that createUnityInstance() returns. For further information on createUnityInstance() see WebGL: Compressed builds and server configuration.


  • Removed asm.js linker target in Unity 2019.1
  • Build file updates and Data Caching added in Unity 2020.1
Building and distributing a WebGL project
Reduce load times with AssetBundles