Lemmy uses [Bootstrap v4](https://getbootstrap.com/), and very few custom css classes, so any bootstrap v4 compatible theme should work fine.
## Creating
- Use a tool like [bootstrap.build](https://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.