[Kiwikwi]

TL;DR: To deploy on mobile, you should compile your Unity project as an app.

Per the manual: "Mobile devices are not supported by Unity WebGL." (https://docs.unity3d.com/Manual/webgl-gettingstarted.html)

You're not just rendering a picture, you're running a full-fledged high-end game engine, in JavaScript (meaning a ~50% slowdown), and using that to render a picture. It is to be expected that even high-end phones will struggle with that.

Unity WebGL is intended to be used as a frictionless way of distributing games to desktop users (think sites like Kongregate). On mobile, the respective app stores arguably already provides a similarly frictionless distribution option... so just build your project as an app.

Alternatively, you can look into lightweight engines that specifically target WebGL. These will usually run just fine on mobile, though they obviously don't offer the same feature set as Unity.

[nkkollaw]

Sorry, it seemed from my comment that we care about mobile, but we'd be happy if this worked on the desktop.

I'm wondering if we can optimize the full-fledged high-end game engine so that some components that are not used are not loaded.