This is sample text demonstrating the current CSS variables in action. Adjust the variables below and watch this area update in real time.
CSS custom properties, commonly known as CSS variables, are a powerful feature introduced in CSS3. They allow developers to define reusable values prefixed with -- (e.g., --color-primary) and reference them via the var() function. Unlike preprocessor variables, CSS variables are dynamically resolved at runtime in the browser, support JavaScript read/write operations, and enable conditional assignment via media queries — making them the ideal solution for theme systems and design tokens.
This CSS Variables Generator is designed to help frontend developers quickly build and manage design token systems. Here is a detailed walkthrough:
Adding Variables: In the Variable Manager section, first select the variable type (Color, Size, Font, or Text), then enter the variable name and value. You do not need to add the -- prefix — the tool handles it automatically. Selecting the Color type reveals a color picker; you can click the swatch to pick a color visually or type a hex/RGB value manually. Press Enter to add quickly.
Editing & Deleting: Added variables appear in the list below. Click any value field to edit it inline — the preview and code output update in real time. Click the Delete button on the right to remove a variable. All changes are instantaneous; there is no save button.
Live Preview: The preview area at the top of the page showcases a set of typical UI components (card, button, badge). All their style properties reference the CSS variables you define. When you change a variable value, the preview immediately reflects the change, letting you visually understand how design tokens affect the overall look.
Preset Themes: The tool includes 8 carefully designed theme presets, covering Modern Blue & Purple, Warm Tones, Forest Green, Dark Theme, Minimal Gray, Cyberpunk, Soft Pastel, and Material Design styles. Click any preset to instantly load a complete variable set — perfect for jumpstarting a new project or serving as design inspiration.
Code Export: When your design is ready, check the CSS Code Output section for the generated :root variable code. Three formats are supported: plain CSS (:root{--var:value}), SCSS ($var: value), and JSON (for cross-platform use). Click any Copy button to copy to clipboard. You can also export/import JSON files for team sharing of design tokens.
CSS variables and design tokens have a wide range of applications in modern frontend development:
Theme Systems & Dark Mode: This is the most classic use case for CSS variables. Define light theme variables in :root, then override the same variable names under [data-theme="dark"]. Since all component styles reference variables via var(), switching themes only requires changing variable definitions — no component styles need to be rewritten. Combined with the prefers-color-scheme media query, the UI can automatically follow the system dark mode setting.
Design System Consistency: Large projects often have dozens of pages and components, making manual color and spacing consistency extremely difficult. With a design token system, teams share a single set of variable definitions — primary color, secondary color, text color, background color, spacing, border radius, shadows, etc. — ensuring visual language consistency across the entire product. Changing a variable value updates everything globally, dramatically reducing maintenance cost.
Multi-Brand / White-Label Customization: For SaaS products or white-label solutions, different clients need different brand colors and themes. Using CSS variables, you simply prepare a set of variable overrides for each client and load them dynamically at runtime to achieve brand customization — no need to compile multiple CSS files. This runtime dynamic switching is impossible with traditional preprocessor variables.
Responsive Design Tokens: CSS variables support reassignment within media queries, meaning you can define different design tokens for different screen sizes. For example, use smaller spacing and font sizes on mobile, and larger values on desktop. This responsive token system makes component adaptation elegant and concise.
Inheritance & Cascade: CSS variables follow standard inheritance and cascade rules. Variables defined on :root (the html element) are global and inheritable by all elements. You can also redefine variables on specific elements, affecting only that element and its children. This local override capability is extremely powerful for nested themes and component-level customization.
The var() Fallback Value: The var() function accepts a second parameter as a fallback, using the syntax var(--name, fallback). When the variable is undefined, the fallback is used. This is very useful for progressive enhancement and third-party component integration. Fallbacks can also be nested: var(--brand, var(--primary, blue)).
Design Token Layer Architecture: Mature design systems typically use a three-tier token architecture: primitive tokens (e.g., --blue-500), semantic tokens (e.g., --color-primary referencing --blue-500), and component tokens (e.g., --button-bg referencing --color-primary). This layered design ensures that global brand changes and component-level customization do not interfere with each other.
Style Dictionary Integration: Style Dictionary is an open-source design token management tool by Amazon that can compile a single JSON token definition into CSS variables, SCSS variables, iOS Swift, Android XML, and other platform formats. The JSON format exported by this tool can be used directly as Style Dictionary input, enabling cross-platform design token synchronization.
CSS variables are dynamically resolved at runtime in the browser, supporting JavaScript read/write, media query conditional assignment, and runtime theme switching. Sass/Less variables are statically replaced at compile time and cannot change after generation. CSS variables are natively supported by browsers with no compilation step. Both can be used together — Sass variables for compile-time logic, CSS variables for runtime theming.
Use document.documentElement.style.setProperty('--var-name', 'newValue') to modify a global variable — all references update automatically. To read, use getComputedStyle(document.documentElement).getPropertyValue('--var-name'). This is the cleanest way to implement a theme switcher.
Nearly all CSS value types are supported: colors (hex/rgba/hsl), lengths (px/rem/vw), percentages, fonts, strings, numbers, calc() expressions, and more. Variables can even store composite values like 0 4px 6px rgba(0,0,0,.1) for use in properties like box-shadow via var().
Use semantic naming rather than specific-value naming. For example, --color-primary is better than --blue-500 because the primary color might change from blue to purple, and the semantic name does not need to change. Common prefixes include color-, bg-, text-, border-, spacing-, radius-, font- to help organize variable categories.
The JSON format contains structured data with variable names, types, and values. It can be used for: 1) importing back into this tool to restore configuration; 2) feeding into Style Dictionary to compile multi-platform tokens; 3) syncing design tokens with design tools (Figma plugins); 4) generating other format configuration files in Node.js scripts.
IE11 does not support CSS custom properties. If IE support is required, you can use the PostCSS plugin postcss-custom-properties to compile CSS variables into static values, though this loses runtime switching capability. Given that IE was officially retired in 2022, modern projects typically no longer support it.