Do game's optimization which only use ugui and deployed by webgl

Unity Engine
1

Well, Im making a 2D game which only use ugui, how to optimize it and remove the redundant things? I noticed that when i scroll the bar in a scroll rect, the webpage begins to be stuck until the bar stopped.

2

You can try Optimizing Unity UI - Unity Learn or watch some of the talks about the UI given by our engineers and other customers like

or

which, while it is about mobile optimization, many things apply to general projects too.

3

Well I found that when I scroll the bar,Canvas.SendWillRenderCanvases()'s GC was 4.9mb…That’s a huge data and i dont know why