I just released QLCodePreview, a free macOS Quick Look extension that syntax-highlights source code right in Finder. On a stock Mac, space-bar on most code files just shows you an icon. With this installed, you get a colorised preview instead.
It's the successor to a plugin fork I've kept alive since 2012. Apple deprecated the old plugin format, and the modern replacement runs in a sandbox that forbids the external tools the old plugin relied on, so I rewrote the whole thing: my own highlighter, 51 languages, and signed and notarized builds you can install with Homebrew.
It's free for personal and noncommercial use, and it stays free. If it saves you time and you feel like tossing a coffee my way, that's what keeps independent Mac software like this sustainable.
And if a coffee isn't your thing, spreading the word is worth just as much. If you know developers or other people who live in Finder on a Mac all day, send it their way.
It's useful for these types of users; Apple-platform developers, infra and DevOps engineers, log readers and support ops, data scientists and academics, web and frontend developers, game developers and makers, functional-language developers, Python library authors, shell and dotfile wranglers.
Word of mouth is how free tools like this find the people who need them.
Either way, grab it and tell me what breaks:
https://konstruukt.com/projects/qlcodepreview/
Brian