Greasy Fork

Example: https://greasyfork.org/en/scripts/411442-flow-youtube-chat/code

Suggest to change to high performance library "CodeMirror" (v5 or v6)

https://codemirror.net/

CodeMirror is designed for high performance coding syntax highlighting

Here is the preview of using Code Mirror

https://greasyfork.org/en/scripts/472051-greasyfork-code-syntax-highlight-by-codemirror

Highlight.js version, supporting javascript, css, stylus, and less

https://greasyfork.org/scripts/481945-greasyfork-code-syntax-highlight-by-highlight-js

Here is the preview of using Code Mirror

https://greasyfork.org/en/scripts/472051-greasyfork-code-syntax-highlight-by-codemirror

This has an annoying cursor with a highlight for no reason,

Highlight.js version, supporting javascript, css, stylus, and less

https://greasyfork.org/scripts/481945-greasyfork-code-syntax-highlight-by-highlight-js

and this messing with a css making a same content take more space

PrismJS version

https://greasyfork.org/scripts/482182-greasyfork-code-syntax-highlight-by-prismjs