Clarification on multisite config and routing setup

Hi everyone,

I’m setting up a Kirby project in multisite mode for the first time and I’d love some clarification.

I didn’t start this project with multisite in mind, so I had to retrofit the setup — which is probably why I ran into quite a bit of routing trouble. I’ve mostly managed to solve it, but I still don’t feel like I fully understand what’s happening.

Specifically, I’m confused about what needs to stay in the root /site folder versus what belongs in the /site-x/site folder.

  • Do config, index.php, routes, helpers, and assets all need to be duplicated per site?

  • Or should some of these only live in the root and others be site-specific?

  • Right now I’ve ended up with a lot of duplication, and the behavior feels unpredictable. I’m not confident that I’m controlling it properly.

This is wasting quite a bit of time and causing some frustration, so I figured it’s better to just ask people with more experience here. Sorry if some of these questions sound basic — the documentation on multisite setup doesn’t go into much detail.

Any pointers or best practices would be greatly appreciated!