WebGL2

WebGL is an API for rendering graphics in web browsers, which is based on the functionality of the OpenGL ES graphics library. WebGLA JavaScript API that renders 2D and 3D graphics in a web browser. The Unity Web 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 2.0 (WebGL2) is the version of WebGL that Unity supports. WebGL2 roughly matches with the OpenGL ES 3.0 functionality.

WebGL2 is widely accepted by most browsers and is the default Web graphics API in Unity.

Browsers with WebGL 2.0 support have the following advantages:

The content in the Standard ShaderA program that runs on the GPU. More info
See in Glossary is of high quality.
Support for GPU Instancing and directional lightmapA 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.
There’s no restrictions on indexing and loops in shader code.
Better performance than base WebGL.

Camera clear

By default, Unity Web clears the drawing buffer after each frame, which means the content of the frame buffer clears regardless of the Camera.clearFlags setting. However, you can change this behavior at instantiation time. To do this, set webglContextAttributes.preserveDrawingBuffer to true in the index.html file of your Web template.

Note : If you set any WebGL context attributes, you must also add a line to preserve the Power Preference Player setting.

script.onload = () => {
  config['webglContextAttributes'] = {
    preserveDrawingBuffer: true, //Add this line to preserve the Camera.clearFlags setting
    powerPreference: {{{ WEBGL_POWER_PREFERENCE }}} //Add this line to preserve the Power Preference Player setting
  };
  createUnityInstance(canvas, config, (progress) => {

Anti-aliasing

WebGL supports anti-aliasing on most (but not on all) combinations of browsers and GPUs.

To enable anti-aliasing:

Go to the Quality Settings (menu: Edit > Project Settings, then select the Quality category).
In the Rendering section, make sure Anti Aliasing isn’t set to Disabled.

For more information about anti-aliasing, refer to the anti-aliasing documentation and Quality Settings.

Web shader code restrictions

The WebGL 2.0 specification imposes some limitations on GLSLS shader code. This is mainly relevant if you write your own shaders. Precision qualifiers WebGL 2.0 requires you to specify the precision of all variables in the shader. You can use highp, mediump, or lowp to specify the precision of the variable. If you don’t specify the precision, the shader will use the default precision, which is mediump. You can also use precision to specify the precision of a block of variables.

Additional resources

Introduction to Web graphics APIs

WebGPU (Experimental)