WebGL runs on the same machine but uses a very different path to the GPU. On Mac, OpenGL is deprecated and the implementation is very outdated and feature poor. WebGL is not deprecated, and uses the ANGLE library to run on top of Metal.
From what I know, OpenGL on macOS is internally implemented using Metal and supports more features than ANGLE.
ANGLE on macOS supports OpenGL ES 3.0 when running using Metal backend (source: https://github.com/google/angle), whereas macOS natively supports Core 4.1.
And from my experience, there is basically no difference in performance between Apple's implementation and ANGLE, especially for simple things like what the author is doing.
I don't have internal knowledge of Apple's implementation but it could potentially be layered on top of Metal for Apple Silicon (probably not for Intel) though if so it probably uses internal-only capabilities not exposed to Metal users.
OpenGL ES 3.0 is newer than OpenGL 4.1. The feature set is broadly very similar. Native macOS OpenGL is a backwards compatibility feature and not intended for new development. Lack of KHR_debug and general bugginess makes it a poor choice for learning OpenGL or deploying software on. On the other hand, WebGL is currently supported and extensively tested, with much better validation and error messages and much (much, much) better cross platform compatibility.
This is false. Source: I added WebGL 2 support to WebKit using ANGLE, with Apple's help (they made ANGLE's Metal backend). Firefox uses ANGLE on every platform for shader translation, and on some platforms it uses ANGLE for the entire API (on others it has a custom OpenGL to WebGL translation layer).
Sure it does. The "ANGLE backend" flag affects everything from frame pacing to whether DRM-protected content can be screenshotted. On websites that don't touch WebGL at all whatsoever.
