A theme designer for Jellyfin 12, delivered as a server plugin. Pick colors, bar layouts and styles, card effects, fonts and dozens of other options in the Dashboard, watch a live preview of the real web client for the web, TV and mobile layouts, and apply with one click.

The output is plain CSS written to Dashboard → General → Branding → Custom CSS - the same place you would paste a hand-written theme. Nothing else in Jellyfin is touched; uninstalling leaves a server that behaves exactly as before. A few features that CSS cannot do (custom toolbar buttons, a home slideshow, card badges, a closable info bar) come from a small client script injected through the File Transformation plugin when it is installed.

From the plugin repository:

In Jellyfin open Dashboard → Plugins → Repositories and add:

https://raw.githubusercontent.com/SpeeDFireCZE/jellycanvas/main/manifest.json

Name it "Jellycanvas" (the name is only shown to you).

Go to Catalog, find Jellycanvas under General and install it.

Restart Jellyfin.

Open Dashboard → My Plugins → Jellycanvas.

Updates appear in the catalog like any other plugin.