HTMLCanvasElement.getContext() - Web APIs
premultipliedalpha: boolean that indicates that the page compositor will assume the drawing buffer contains colors with pre-multiplied alpha.

OffscreenCanvas.getContext() - Web APIs
premultipliedalpha: boolean that indicates that the page compositor will assume the drawing buffer contains colors with pre-multiplied alpha.

WebGLRenderingContext.getContextAttributes() - Web APIs
anvas"></canvas> and given this webgl context var canvas = document.getelementbyid('canvas'); var gl = canvas.getcontext('webgl'); gl.getcontextattributes(); the getcontextattributes method returns an object that describes the attributes set on this context, for example: { alpha: true, antialias: true, depth: true, failifmajorperformancecaveat: false, powerpreference: "default", premultipliedalpha: true, preservedrawingbuffer: false, stencil: false, desynchronized: false } the context attributes can be set when creating the context using the htmlcanvaselement.getcontext() method: canvas.getcontext('webgl', { antialias: false, depth: false }); see getcontext() for more information about the individual attributes.

XRWebGLLayer.framebuffer - Web APIs
the xr compositor assumes that opaque framebuffers use colors with premultiplied allpha, regardless of whether or not the webgl context's premultipliedalpha context attribute is set.