lemmy/docs/src/contributing_theming.md

Theming Guide

Lemmy uses Bootstrap v4, and very few custom css classes, so any bootstrap v4 compatible theme should work fine.

Creating

• Use a tool like bootstrap.build to create a bootstrap v4 theme. Export the bootstrap.min.css once you're done, and save the _variables.scss too.

Testing

• To test out a theme, you can either use your browser's web tools, or a plugin like stylus to copy-paste a theme, when viewing Lemmy.

Adding

1. Copy {my-theme-name}.min.css to ui/assets/css/themes. (You can also copy the _variables.scss here if you want).
2. Go to ui/src/utils.ts and add {my-theme-name} to the themes list.
3. Test locally
4. Do a pull request with those changes.