Reading is personal. In diffwiki the author writes the content, but how you read it is your choice — customizable like your editor's colorscheme. Two people reading the same published wiki can read it in completely different themes, and neither changes the other's experience or the underlying markdown.
Pick a theme
Open the settings dialog (the gear in the top navigation) to choose from 30+ built-in themes — default, catppuccin, claude, graphite, cyberpunk, nature, mono, and many more. Each theme is a full look: it sets the color palette and the typography (its own sans, serif, mono, and heading fonts), so switching themes restyles the whole reading surface at once. A live swatch previews each theme in its own colors before you apply it.
Light, dark, or system
Independently of the theme, choose a color mode: Light, Dark, or System. System follows your operating system's appearance and updates live when your OS flips between light and dark.
Your preferences, not the author's
Theme and mode are stored locally in your browser — they are a per-reader setting, never baked into the published site. This is the point: your reading experience belongs to you, the way an editor's theme belongs to you, not to the person who wrote the file.
More reading customization is on the way — remembered per-reader state, and keyboard-driven navigation with full Helix key bindings. See the Roadmap.