Theming & Styling

Inspector Lab's theming system is built on a carefully designed architecture that allows the DevTools-styled inspector to adapt seamlessly between light and dark modes, and to optionally swap in the extension's own branding palette.

Theme Gallery

The four theme variants side by side — the branded palette and the classic Chrome DevTools look, each in light and dark mode:

The inspector with the branded theme in light mode — Branded theme in light and dark mode

The inspector with the branded theme in dark mode — Branded theme in light and dark mode

The inspector with the classic Chrome DevTools style in light mode — Classic Chrome DevTools style in light and dark mode

The inspector with the classic Chrome DevTools style in dark mode — Classic Chrome DevTools style in light and dark mode

Architecture Overview

The theme system consists of three main layers:

Base Design Tokens — Metrics (typography, spacing, sizing) and colors organized under the DevtoolsTokens interface
Theme Variants — Light, dark, and branded combinations that apply tokens consistently
Styled Components — Reusable CSS building blocks that consume tokens from theme.devtools

This separation ensures that every UI surface—the popup, the inspector panel, dialogs—reads the same values and stays in sync across modes.

Design Tokens

<Field value="DevtoolsTokens" type="interface" required> The complete set of design tokens available to styled components. Organized into typography, spacing, colors, and syntax highlighting. </Field>

Typography

Token	Default	Purpose
`fontFamily`	System sans stack	UI chrome: toolbars, tabs, labels
`monoFamily`	Monospace stack	Code, DOM nodes, computed values, console output
`fontSize`	`12px`	General UI text size
`fontSizeSmall`	`11px`	Secondary labels, headers
`monoFontSize`	`11px`	Monospace text (syntax, values)
`lineHeight`	`1.4`	Line spacing across all text

The two font stacks in full:

fontFamily: '-apple-system, BlinkMacSystemFont, "Segoe UI", system-ui, sans-serif',
monoFamily: 'Menlo, Monaco, "SF Mono", "Roboto Mono", Consolas, "Liberation Mono", "Courier New", monospace',

Spacing & Sizing

Token	Default	Purpose
`toolbarHeight`	`27px`	Height of toolbar rows and main tab strip
`tabHeight`	`27px`	Tab button height
`rowHeight`	`15px`	Single dense tree/grid row
`treeIndent`	`12px`	Horizontal offset per DOM tree depth level
`touchTarget`	`24px`	Finger-sized tap area on touch devices

Colors

The default light mode mirrors Chrome DevTools' own palette. Dark mode and branded variants derive all their colors from the same tokens:

interface DevtoolsTokens {
  // Panel & control backgrounds
  surface: string;              // Panel body background (white/dark)
  surfaceSubtle: string;        // Recessed background for sidebars
  toolbar: string;              // Toolbar and tab strip background

  // Text colors
  text: string;                 // Primary text
  textSubtle: string;           // Secondary / disabled text
  textDisabled: string;         // Low-contrast text
  
  // Interaction colors
  accent: string;               // Primary interactive color (blue)
  accentSubtle: string;         // Accent with reduced opacity
  onAccent: string;             // Text/glyphs on accent background
  focusRing: string;            // Focus outline color

  // Tab and row states
  tabSelectedText: string;      // Selected tab color
  tabHoverBackground: string;   // Tab hover fill
  tabIndicator: string;         // 3px slider bar under tab
  rowHover: string;             // Row hover background
  rowSelected: string;          // Selected row (focused)
  rowSelectedBlur: string;      // Selected row (blurred)

  // Borders
  border: string;               // 1px separators
  borderStrong: string;         // Heavier pane split borders
}

Syntax Highlighting

Code in the Elements and Sources panels uses a dedicated palette:

syntax: {
  tag: string;              // HTML/XML tag names
  attributeName: string;    // Attribute identifiers
  attributeValue: string;   // Quoted attribute values
  text: string;             // Text node content
  comment: string;          // <!-- comments -->
  doctype: string;          // <!DOCTYPE>
  punctuation: string;      // Brackets, angle brackets
  property: string;         // CSS property names
  value: string;            // CSS property values
  number: string;           // Numeric literals
  string: string;           // String literals
  keyword: string;          // Keywords (class, id, etc.)
}

Status Colors

Console messages and Network statuses use semantic colors:

status: {
  error: string;
  errorBackground: string;
  errorBorder: string;
  warning: string;
  warningBackground: string;
  warningBorder: string;
  info: string;
  success: string;
}

Box Model Diagram

The Computed panel's box-model visualization uses pastel fills (identical across light and dark modes for consistency):

boxModel: {
  margin: string;      // #f9cc9d (orange)
  border: string;      // #fdd291 (yellow)
  padding: string;     // #c3d08b (green)
  content: string;     // #a1c2cf (blue)
  text: string;        // #222222 (always dark for readability)
}

Theme Variants

Inspector Lab provides four complete theme configurations:

<Tabs> <TabContent title="Light (Default)"> The default light theme mirrors Chrome DevTools' own baseline-grayscale skin: white surface, light gray toolbars, blue accents.

export const theme: AppTheme = {
  ...base,
  colors: brandColorsLight,
  fonts: { ...base.fonts, ...brandFonts },
  devtools: devtoolsLight,
};

</TabContent>

<TabContent title="Dark"> Dark mode inverts the palette: dark surfaces, darker toolbars, light blue accents. Uses the same metrics as light so UI density is identical.

export const themeDark: AppTheme = {
  ...baseDark,
  colors: brandColorsDark,
  fonts: { ...baseDark.fonts, ...brandFonts },
  devtools: devtoolsDark,
};

</TabContent>

<TabContent title="Branded Light"> The popup's "custom inspector theme" toggle swaps in the extension's own branding palette (teal primary, amber secondary). All colors derive from the Cherry theme—the inspector and popup can never drift apart.

export const themeBranded: AppTheme = {
  ...theme,
  devtools: brandDevtools(brandColorsLight, false),
};

</TabContent>

<TabContent title="Branded Dark"> Branded palette in dark mode. Maintains the same semantic color meanings as the default dark theme (light accents on dark surfaces) while swapping the hue.

export const themeDarkBranded: AppTheme = {
  ...themeDark,
  devtools: brandDevtools(brandColorsDark, true),
};

</TabContent> </Tabs>

Theme Resolution

The active theme is determined by the user's color-scheme preference and branding toggle:

export function resolveInspectorTheme(
  isDark: boolean,
  branded: boolean,
): AppTheme {
  if (branded) return isDark ? themeDarkBranded : themeBranded;
  return isDark ? themeDark : theme;
}

The ThemeProvider component reads the initial preference from localStorage.theme (or falls back to the OS color-scheme preference) and applies it via cherry-styled-components' ClientThemeProvider:

function resolveInitialTheme(): "light" | "dark" {
  try {
    const stored = localStorage.theme;
    if (stored === "dark" || stored === "light") return stored;
  } catch {
    // Fall back to the operating-system preference.
  }

  return window.matchMedia?.("(prefers-color-scheme: dark)").matches
    ? "dark"
    : "light";
}

export function ThemeProvider({ children }: { children: ReactNode }) {
  return (
    <ClientThemeProvider
      theme={theme}
      themeDark={themeDark}
      $initial={INITIAL_THEME}
      $themeColor={false}
    >
      {children}
    </ClientThemeProvider>
  );
}

Styled Component Building Blocks

All DevTools panels are assembled from reusable CSS mixins and styled components, ensuring consistency across surfaces and modes. Every mixin reads from theme.devtools:

Typography Mixins

devtoolsUi — System sans font for UI chrome (toolbars, tabs, labels):

export const devtoolsUi = css`
  color: ${({ theme }) => theme.devtools.text};
  font-family: ${({ theme }) => theme.devtools.fontFamily};
  font-size: ${({ theme }) => theme.devtools.fontSize};
  line-height: ${({ theme }) => theme.devtools.lineHeight};
`;

devtoolsMono — Monospace font for code, values, and console output:

export const devtoolsMono = css`
  color: ${({ theme }) => theme.devtools.text};
  font-family: ${({ theme }) => theme.devtools.monoFamily};
  font-size: ${({ theme }) => theme.devtools.monoFontSize};
  line-height: ${({ theme }) => theme.devtools.rowHeight};
`;

Scrollbar Styling

devtoolsScrollbar — Slim overlay scrollbar (Firefox and WebKit):

export const devtoolsScrollbar = css`
  scrollbar-width: thin;
  scrollbar-color: ${({ theme }) => theme.devtools.scrollbarThumb} transparent;

  &::-webkit-scrollbar {
    width: 10px;
    height: 10px;
  }

  &::-webkit-scrollbar-thumb {
    background: ${({ theme }) => theme.devtools.scrollbarThumb};
    background-clip: padding-box;
    border: solid 2px transparent;
    border-radius: 10px;
  }
  /* ... */
`;

Touch & Interaction

touchHitArea(anchor) — Finger-sized tap area drawn as a pseudo-element (no layout cost):

The DevTools inspector runs on iPads where a 15px row is unhittable. Row density is preserved by growing a 24px hit area as an absolutely positioned ::after pseudo-element anchored to the nearest container edge.

export const touchHitArea = (anchor: "left" | "right") => css`
  &::after {
    content: "";
    position: absolute;
    top: 50%;
    ${anchor}: 0;
    width: ${({ theme }) => theme.devtools.touchTarget};
    height: ${({ theme }) => theme.devtools.touchTarget};
    transform: translateY(-50%);
  }
`;

rowActionButton(size) — Hover-revealed per-row action (delete, edit):

Row actions start invisible and reveal on hover, focus, or on devices with no hover capability:

export const rowActionButton = (size: number) => css`
  button {
    position: relative;
    width: ${size}px;
    height: ${size}px;
    /* ... */
    opacity: 0;
    pointer-events: none;

    /* Focus reveals the button so keyboard never chases invisibility. */
    &:focus-visible {
      outline: solid 1px ${({ theme }) => theme.devtools.focusRing};
      outline-offset: -1px;
      opacity: 1;
      pointer-events: auto;
    }
  }

  /* No hover capability: show always. */
  @media (hover: none) {
    button {
      opacity: 1;
      pointer-events: auto;
    }
  }
`;

Form Control Overrides

devtoolsCheckbox — Restyles Cherry's checkbox into a compact 12px box:

export const devtoolsCheckbox = css`
  && input {
    width: 12px;
    height: 12px;
    background: transparent;
    border: solid 1px ${({ theme }) => theme.devtools.textSubtle};
    border-radius: 2px;
  }

  && input:checked {
    background: ${({ theme }) => theme.devtools.accent};
    border-color: ${({ theme }) => theme.devtools.accent};
  }

  && svg {
    width: 8px;
    height: 8px;
    color: ${({ theme }) => theme.devtools.onAccent};
  }
`;

DevtoolsField — Shrinks Cherry form controls from 40px to 19px (DevTools' compact scale):

Borderless variant ($plain) for the console prompt and editable grid cells:

<DevtoolsField $plain>
  {/* Input inherits font from surrounding surface */}
</DevtoolsField>

DevtoolsButtonGroup — Text buttons (20px height) for panels and dialogs:

export const DevtoolsButtonGroup = styled.div`
  button {
    height: 20px;
    padding: 0 8px;
    background: ${({ theme }) => theme.devtools.toolbar};
    border: solid 1px ${({ theme }) => theme.devtools.border};
    border-radius: 2px;
    /* ... */
  }
`;

Layout Components

Component	Purpose
`InspectorWindow`	Whole floating window: flat, square-cornered DevTools frame with optional shadow
`WindowToolbar`	Top row: picker controls, tab strip, window actions; also the drag handle
`TabStrip`	Main tabs (Elements, Console, Network, etc.)
`Tab`	Single tab button with 3px rounded slider indicator
`PanelHost`	Container for the active panel
`Panel`	Panel's root: fills the window and scrolls internally
`PanelToolbar`	Secondary toolbar inside a panel (filters, actions)
`SplitView` / `SplitMain` / `SplitSidebar`	Three-column layout (main + sidebar)
`Scroller`	Any scrolling region inside a panel
`SubTabBar` / `SubTab`	Sub-tabs (Styles / Computed, underlined not filled)
`PaneHeader`	Collapsible section heading inside a sidebar
`DataGrid`	Network request table, styled like DevTools' data grid
`GridRow` / `GridActionCell`	Table row with hover-revealed actions
`EmptyState`	Centered placeholder (no elements matched, no console output, etc.)
`StatusBar`	Bottom strip (breadcrumbs, request totals)

Branded Theme Derivation

The branded theme is computed dynamically from the Cherry palette, ensuring the popup and inspector stay in sync. All branded colors derive from these functions:

const mix = (color: string, percent: number, into: string) =>
  `color-mix(in srgb, ${color} ${percent}%, ${into})`;

function brandDevtools(
  colors: Theme["colors"],
  isDark: boolean,
): DevtoolsTokens {
  const statusInk = (color: string) =>
    isDark ? tint(color, 30) : shade(color, 30);

  return {
    surface: colors.light,
    toolbar: isDark
      ? colors.grayLight
      : mix(colors.primary, 8, colors.light),
    border: isDark ? colors.gray : colors.grayLight,
    accent: colors.primary,
    // ... all other tokens computed from palette
  };
}

The box-model diagram colors (margin orange, padding green, border yellow, content blue) are the one exception: they are not derived from the palette and stay identical across all four variants, so the Computed panel's visualization remains instantly recognizable in any mode.