Themes

Lantern uses embedded Base16 themes.

Each theme defines 16 colors, then lantern maps those colors to slide content, syntax highlighting, admonitions, and UI chrome.

Available themes

Built-in theme names:

• catppuccin-latte
• catppuccin-frappe
• catppuccin-macchiato
• catppuccin-mocha
• gruvbox-material-dark
• gruvbox-material-light
• nord
• nord-light
• oxocarbon-dark
• oxocarbon-light
• rose-pine
• rose-pine-dawn
• rose-pine-moon
• solarized-dark
• solarized-light

default is also accepted. It resolves to oxocarbon-dark or oxocarbon-light based on terminal background detection.

Named themes are loaded from the user config directory first, then from the built-in list. Unknown theme names fail with an error when presenting or printing.

Using a theme

Front matter

---
theme: catppuccin-mocha
---

# First slide

TOML front matter works too:

+++
theme = "nord"
+++

# First slide

Command line

lantern present presentation.md --theme nord
lantern print presentation.md --theme catppuccin-latte
lantern present presentation.md --theme-file ./my-theme.yml

User config directory

Put Base16 YAML themes in one of these directories and reference them by file stem with --theme or front matter:

• $LANTERN_CONFIG_HOME/themes
• $XDG_CONFIG_HOME/lantern/themes
• ~/.config/lantern/themes

For example, ~/.config/lantern/themes/acme.yml can be used as --theme acme or theme: acme.

Environment variable

export SLIDES_THEME=gruvbox-material-dark
lantern present presentation.md

Theme priority

Lantern resolves the theme in this order:

1. --theme-file on the command line
2. --theme on the command line
3. theme in front matter
4. SLIDES_THEME
5. Detected default, oxocarbon-dark or oxocarbon-light

Base16 mapping

Content colors:

• Headings: base0D
• Body text: base05
• Bold text: base0E
• Italic text: base09
• Code blocks: base0B
• Inline code background: base02
• Links: base0C
• List markers: base0A
• Rules, borders, and dimmed text: base03

UI colors:

• UI background: base00
• Borders and status bar background: base02
• UI titles: base06
• UI text: base05

Admonition colors:

• Note: base0D
• Tip: base0E
• Warning: base0A
• Danger: base08
• Success: base0B
• Info: base0C

Validate a theme file

Lantern can validate a Base16 YAML file:

lantern check --theme theme.yml

Custom theme files can be validated, but rendering still uses built-in themes. The same file shape can be rendered with --theme-file or from the user config theme directory.

A valid theme uses this shape:

system: "base16"
name: "My Theme"
author: "Your Name"
variant: "dark"
palette:
  base00: "#1a1b26"
  base01: "#16161e"
  base02: "#2f3549"
  base03: "#444b6a"
  base04: "#787c99"
  base05: "#a9b1d6"
  base06: "#cbccd1"
  base07: "#d5d6db"
  base08: "#c0caf5"
  base09: "#a9b1d6"
  base0A: "#0db9d7"
  base0B: "#9ece6a"
  base0C: "#b4f9f8"
  base0D: "#2ac3de"
  base0E: "#bb9af7"
  base0F: "#f7768e"

Rendering notes

The printer and TUI use Unicode symbols for readable terminal output:

• ▉ ▓ ▒ ░ ▌ for heading levels
• ─ and ═ for horizontal rules
• │ for blockquotes and table dividers
• • for unordered lists

Code blocks use Syntect for syntax highlighting. Lantern chooses a light or dark Syntect theme based on the active lantern theme variant.