Observable Framework 1.6.0 GitHub️ 1.8k


Themes affect the visual appearance of pages by specifying colors and fonts, or by augmenting default styles. Framework includes several built-in themes, but you can also design your own themes by specifying a custom stylesheet.

The theme is typically set via the theme config option, such as:

theme: "cotton"

You can also apply a theme to an individual page via the front matter:

theme: [glacier, slate]

Here is an overview of the available themes.

Light mode

The built-in light-mode color themes are:

Dark mode

The built-in dark-mode color themes are:

Auto mode

When both a light and a dark mode theme are specified, theme styles are applied selectively based on the user’s preferred color scheme. This is implemented via prefers-color-scheme and typically relies on the user’s operating system settings.

On macOS, you can create a menubar shortcut to quickly toggle between light and dark mode. This is useful for testing.
Designing charts that work well in both light and dark mode can be challenging. If you’d prefer to design for only one mode, set the theme explicitly to light or dark.


Theme modifiers are intended to compose with the above color themes. They are:

The alt theme swaps the page and card background colors. This brings cards to the foreground and is recommended for dashboards.

The wide theme removes the maximum width constraint of the main column, which is normally 1152 pixels, allowing it to span the full width of the page. This is recommended for dashboards and is typically combined with the alt theme modifier and toc: false to disable the table of contents.

The dashboard theme alias composes the default light and dark themes (air and near-midnight) with the alt and wide modifiers. On its own, dashboard is equivalent to [light, dark, alt, wide].


In addition to themes and theme modifiers, there are special aliases:

On its own, default is equivalent to [light, dark] (or [air, near-midnight]). The default theme is applied by default if you don’t specify any color theme. You can also use default to combine a specific light or dark theme with the default theme of the opposing mode; for example [cotton, default] is equivalent to [cotton, dark], and [coffee, default] is equivalent to [coffee, light].


The following custom properties are defined by the current theme:

Name Color Description
page foreground color
page background color
block background color
heading foreground color
secondary text foreground color
faint border color
fainter border color
faintest border color
emphasis foreground color

You can use these properties anywhere you like. For example, to style a line chart to match the focus color:

Plot.lineY(aapl, {x: "Date", y: "Close", stroke: "var(--theme-foreground-focus)"}).plot()

A handful of color classes are also provided:

<div class="red">I am red text.</div>
<div class="yellow">I am yellow text.</div>
<div class="green">I am green text.</div>
<div class="blue">I am blue text.</div>
<div class="muted">I am muted text.</div>