Jetons primitifs et sémantiques

Design tokens are named values that store the visual decisions of a design system — colors, spacing, font sizes, and more. Instead of hardcoding #3b82f6 throughout your CSS, you give it a name and reference that name everywhere. This creates a single source of truth that is easy to update globally. Tailwind's config is a natural home for design tokens because it generates utility classes from those named values.

Primitive tokens are raw, descriptive values with no semantic meaning attached. They describe what a value is, not where it is used. Examples include color.blue.500, spacing.4, or fontSize.lg. Tailwind's default color palette is built entirely from primitives — blue-500, red-300, and so on. You reference primitives to build the higher-level semantic layer.

Semantic tokens describe the purpose of a value, not its raw appearance. Instead of blue-500, you would define color.primary. Instead of red-500, you would define color.danger. Semantic tokens make your codebase intent-driven — a developer reading text-primary immediately understands it is the main brand color, regardless of what that color actually is. This abstraction is what enables easy theming and rebanding.

A robust token system uses two layers: primitives at the bottom and semantics on top. The primitive layer stores every raw value your design might ever use. The semantic layer maps those primitives to purpose-driven names. When your brand color changes, you update the primitive once, and every semantic token that references it inherits the change automatically. This separation of concerns is central to scalable design systems.

Once semantic tokens are registered in your Tailwind config, they become available as utility classes across all color-accepting utilities. You can use bg-primary, text-primary, border-primary, and ring-primary — all referring to the same semantic value. This means changing the primary color in your config instantly updates every element in your UI that uses these semantic utilities.

Good token naming follows a consistent pattern that communicates role and scale. A common convention uses category.role.modifier — for example color.action.default, color.action.hover, and color.action.disabled. Avoid overly specific names like submit-button-blue — they break the moment you want to reuse the token elsewhere. Choose names that describe intent and scale, not visual implementation.

The cleanest way to maintain the two-layer architecture is to define your primitives as JavaScript constants in a separate file and import them into your Tailwind config. This keeps primitives readable and reusable while the config itself only contains semantic mappings. When a designer changes the brand palette, only the primitives file needs to be updated — the semantic mapping stays intact.

Tokens are not limited to colors. You can define semantic spacing and typography tokens too. Instead of p-4, a semantic spacing token named card-padding communicates what the spacing is for. In Tailwind, you add these under theme.extend.spacing and theme.extend.fontSize. This ensures UI consistency: every card in the app uses the same p-card padding, and that padding only needs to be adjusted once.

Defining tokens for interactive states is equally important. A primary button needs tokens for its default, hover, active, and disabled appearances. Without semantic tokens, each developer might pick slightly different shades for hover, creating visual inconsistency. With semantic tokens like action-hover and action-disabled, every button in the system responds identically to user interaction.

Semantic tokens shine brightest when combined with dark mode. A primitive token like blue-500 has a fixed value, but a semantic token like primary can map to different primitives in light and dark mode. Using CSS variables as the bridge allows runtime switching without regenerating CSS. This technique is explored further in the theming module, but understanding that semantic tokens enable it is a key architectural insight.

As a design system grows, token audits become essential. An audit checks whether every token is actively used, whether any tokens have drifted from their documented purpose, and whether new patterns have emerged that need a new token. Tools like grep or dedicated design token managers can scan your codebase for unused tokens. Removing unused tokens keeps the config lean and reduces cognitive load for new developers joining the team.

In this lesson you learned: primitive tokens are raw named values like color.blue.500, semantic tokens map those primitives to intent-driven names like color.primary, and two-layer architecture separates what a value is from where it is used. Next up we explore how CSS variables bridge Tailwind tokens with runtime theme switching.