Currently the Editor’s Preview Rendering Level doesn’t have an option for WebGL 2.0 / Feature Level ES3.0. Our choices are “Default Mobile / HTML5 Preview” which is Feature Level ES2.0 and “Default High-End Mobile” which is Feature Level ES3.1. There doesn’t seem to be something that accurate displays what WebGL 2.0 Feature Level ES3.0 will look like.
I have some shaders that work fine on “Default High-End Mobile” (ES3.1) but fail on “Default Mobile / HTML5 Preview” (ES2.0). When I package the HTML5 project with WebGL 2.0, the result in my browser looks like the ES2.0 with the fail shaders.