I have created userscripts to ease logging in my accounts on some websites, but now I'm concerned: Can a site owner see the code of my userscripts?
I'm using Tampermonkey extension for Edge/Chrome, and "Userscripts" Extension/App for iOS Safari.
Usually, websites don't & can't detect userscripts. It all depends on how the userscript code is written and if the website is aware of the such userscript to look for it.
You can read the reply in @grant directive and detecting a user script by a page which should explain it further.