> ## Documentation Index
> Fetch the complete documentation index at: https://celerity-wiki.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Celerity Themes: Dark, Light, Void, and System Preference

> Switch between Celerity Dark, Light, Void, and System preference themes to match your style and environment — changes apply instantly across all open tabs.

Celerity ships with four themes that cover the full range from bright to deep-black. You can switch themes at any time from the Settings panel, and the change takes effect immediately — no save button, no page reload required.

## Available themes

> **System preference**
>
> Follows your operating system's light or dark setting automatically. If you change your OS theme while a Celerity tab is open, the extension updates in real time without any manual action.

> **Celerity Dark**
>
> A dark background optimised for low-light environments. A good all-day choice if you prefer dark interfaces regardless of the time of day.

> **Celerity Light**
>
> A light background suited to bright environments or users who prefer light interfaces. Matches the look of most daytime desktop setups.

> **Celerity Void**
>
> The deepest, darkest option — a near-black surface that minimises any light output. Ideal for distraction-free focus or very low-light settings.

## How to change the theme

**1. Open Settings**

Click the **gear icon** (⚙) in the top-right corner of the new tab page to open the Settings panel.

**2. Find the Theme section**

Scroll down to the **Theme** heading inside the Settings panel.

**3. Select a theme**

Open the dropdown and choose one of the four options: **System preference**, **Celerity Dark**, **Celerity Light**, or **Celerity Void**.

**4. Done**

The theme applies instantly. Close Settings with the **✕** button or press <kbd>Escape</kbd> to return to the shortcut grid.

## Cross-tab synchronisation

Celerity keeps all open new tab pages in sync. When you change the theme in one tab, every other open Celerity tab updates to match — you never end up with a mix of themes across windows.

> [!NOTE]
>
> Theme changes propagate via the browser's `storage` event, so synchronisation only works between tabs in the same browser profile.

## Theme persistence

Your selected theme is saved to `localStorage` under the key `selectedTheme`. It persists between browser sessions, so Celerity opens with your chosen theme on every new tab — including after a browser restart.

The theme is applied at page parse time, before the page body is rendered, which means there is no flash of the default theme on load. Pages restored from the browser's back/forward cache also re-apply your saved theme when they become visible again.

> [!TIP]
>
> If you choose **System preference**, Celerity listens for OS-level light/dark changes and updates the theme live. Switching your OS appearance while Celerity is open requires no manual change inside the extension.


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