WebGLRenderingContext.drawingBufferHeight

The read-only WebGLRenderingContext.drawingBufferHeight property represents the actual height of the current drawing buffer. It should match the height attribute of the <canvas> element associated with this context, but might differ if the implementation is not able to provide the requested height.

Given this <canvas> element:

<canvas id="canvas"></canvas>

You can get the height of the drawing buffer with the following lines:

var canvas = document.getElementById('canvas');
var gl = canvas.getContext('webgl');
gl.drawingBufferHeight; // 150

• WebGLRenderingContext.drawingBufferWidth
• WebGLRenderingContext.viewport()