Text Copied to Clipboard Doesn't Come Outside the Game

When I build the game for WebGL and copy a text, whether directly to systemCopyBuffer or from an Input Field, I can only paste the text inside the game. If I try to paste it to a notepad for example it doesn't work. But it works when I run the game in editor. How can I fix this?

 

This isn't really a UI Toolkit issue, it's a WebGL security feature IIRC. I believe in order to copy from a WebGL app to your system's clipboard you'd need to use a Javascript library or something to bridge that gap.

Google for "Unity WebGL copy to windows clipboard" or something, and you'll find a few workarounds.