WebGL Graphics

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 is an API for renderingThe process of drawing graphics to the screen (or to a render texture). By default, the main camera in Unity renders its view to the screen. More info
See in Glossary graphics in web browsers, which is based on the functionality of the OpenGL ES graphics library. WebGL 1.0 roughly matches OpenGL ES 2.0 functionality, and WebGL 2.0 roughly matches OpenGL ES 3.0 functionality.

Camera Clear

The default WebGL behaviour is to clear the drawing buffer after each frame. This means on Unity WebGL, the content of the frame buffer clears regardless of the Camera.clearFlags setting. However, you can change this behaviour at instantiation time. To do this, set webglContextAttributes.preserveDrawingBuffer to true in your WebGL template:

UnityLoader.instantiate("unityContainer", "%UNITY_WEBGL_BUILD_URL%", {
    Module: {
        "webglContextAttributes": {"preserveDrawingBuffer": true},
    }
});

Deferred Rendering

Unity WebGL only supports Deferred Rendering Path if WebGL2.0 is available. On WebGL1.0, Unity WebGL runtime will fallback to Forward RenderingA rendering path that renders each object in one or more passes, depending on lights that affect the object. Lights themselves are also treated differently by Forward Rendering, depending on their settings and intensity. More info
See in Glossary.

Global Illumination

Unity WebGL only supports baked GI. Realtime GI is not currently supported in WebGL. Furthermore, only Non-Directional lightmapsA pre-rendered texture that contains the effects of light sources on static objects in the scene. Lightmaps are overlaid on top of scene geometry to create the effect of lighting. More info
See in Glossary are supported.

Linear Rendering

Unity WebGL only supports linear color space rendering with WebGL 2.0. Linear color space rendering doesn’t have fallback support for WebGL 1.0. To build a WebGL player using linear color space rendering, you need to remove WebGL 1.0 API in the Player settings, open the Other Settings panel, disable the Automatic Graphics API setting.

Some web browsers don’t support sRGB DXT texture compression. This can decrease the quality of rendering performance when using linear rendering, due to runtime decompression of all the DXT textures.

MovieTextures

WebGL does not support playing Video using the MovieTexture class. However, you can efficiently play back video in your WebGL content using the HTML5 video element. Download this Asset Store package for an example of how to do so.

WebGL Shader code restrictions

The WebGL 1.0 specification imposes some limitations on GLSLS shaderA small script that contains the mathematical calculations and algorithms for calculating the Color of each pixel rendered, based on the lighting input and the Material configuration. More info
See in Glossary code, which are more restrictive than many OpenGL ES 2.0 implementations. This is mostly relevant when you write your own shaders.

Specifically, WebGL has restriction on which values can be used to index arrays or matrices: WebGL only allows dynamic indexing with constant expressions, loop indices or a combination. The only exception is for uniform access in vertex shadersA program that runs on each vertex of a 3D model when the model is being rendered. More info
See in Glossary, which can be indexed using any expression.

Also, restrictions apply on control structures. The only type of loops which are allowed are counting for loops, where the initializer initializes a variable to a constant, the update adds a constant to or subtracts a constant from the variable, and the continuation test compares the variable to a constant. for loops which don’t match those criteria and while loops are not allowed.

Font rendering

Unity WebGL supports dynamic font rendering like all Unity platforms. However, it does not have access to the fonts installed on the user’s machine, so any fonts used must be included in the project folder (including any fallback fonts for international characters, or bold/italic versions of fonts), and set up as fallback font names.

Anti-Aliasing

WebGL supports anti-aliasing on most (but not on all) combinations of browsers and GPUs. To use it, anti-aliasing must be enabled in the default Quality setting for the WebGL platform.

Note that on WebGL1.0 there are several limitations:

• Switching Quality settings at runtime will not enable or disable anti-aliasing. It has to be set up in the default Quality setting loaded at player start up.

• The different multi sampling levels (2x, 4x, etc..) have no effect in WebGL, it’s either on or off.

• Any post-processing effect applied to the cameraA component which creates an image of a particular viewpoint in your scene. The output is either drawn to the screen or captured as a texture. More info
  See in Glossary disables the built-in Anti-Aliasing.

• HDRhigh dymanic range
  See in Glossary is not compatible with anti-aliasing so make sure the Allow HDR camera option is disabled.

There are no such limitations on WebGL2.0.

Reflection Probes

Reflection probes are supported in WebGL, but due to limitations in the WebGL specification about rendering to specific mipmaps, smooth realtime reflection probesA rendering component that captures a spherical view of its surroundings in all directions, rather like a camera. The captured image is then stored as a Cubemap that can be used by objects with reflective materials. More info
See in Glossary are not supported (so realtime reflection probes will always generate sharp reflections, which may appear very low-resolution). Smooth realtime reflection probes will require WebGL 2.0.

WebGL 2.0 support

Unity includes support for the WebGL 2.0 API, which brings OpenGL ES 3.0-level rendering capabilities to the web.

By default, Unity WebGL builds support both WebGL 1.0 and WebGL 2.0 APIs, This can be configured in the WebGL Player settings under the Other Settings panel by disabling the Automatic Graphics API property.

When WebGL 2.0 is supported in browsers, content can benefit from a better quality in the Standard ShaderA built-in shader for rendering real-world objects such as stone, wood, glass, plastic and metal. Supports a wide range of shader types and combinations. More info
See in Glossary, GPU Instancing support, directional lightmap support, no restrictions on indexing and loops in shader code, and better performance.

You can use SystemInfo.graphicsDeviceType at run time to determine whether the Unity instance is rendering with OpenGLES3 (WebGL2.0) or OpenGLES2 (WebGL1.0).

• 2018–10–26 Page amended with limited editorial review

• Linear rendering for WebGL 2.0 added in 2017.2 NewIn20172