styled-components / Emotion to CSS

Paste styled-components or Emotion code and get plain CSS back — class names derived from variable names, nested & selectors expanded, and simple ${...} interpolations converted to CSS custom property comments. Useful when migrating away from CSS-in-JS to vanilla CSS or CSS Modules.

How to use the styled-components / Emotion to CSS

1. Paste styled-components or Emotion source code — const Name = styled.tag`...` blocks, css`...` blocks, or both. 2. Click Convert. The tool extracts each template literal, derives a CSS class name from the variable name (e.g. const PrimaryButton → .PrimaryButton), expands & pseudo-selectors into flat rules, and converts simple prop interpolations into a CSS custom property comment. 3. Copy the output and paste it into your CSS file. 4. In your components, replace <Button> with <button className="Button">. The Example button loads a realistic styled-components snippet with nested selectors and one interpolation.

What is CSS-in-JS and why migrate to plain CSS?

styled-components and Emotion are CSS-in-JS libraries that let you write CSS inside JavaScript template literals. They generate class names at runtime, scope styles to components, and support dynamic values via JavaScript interpolations. For many projects they are a good fit, but there are growing reasons to migrate: bundle size (styled-components 5 adds ~13 kB gzipped), runtime overhead (class generation and style injection happen on every render), streaming SSR complications, and React Server Components incompatibility (as of React 18, CSS-in-JS libraries that require the runtime do not work in Server Components).

Plain CSS, CSS Modules, or utility-class approaches (Tailwind) avoid all of these constraints: styles are static, sent as a separate file, cached by the browser, and have no runtime cost. The migration involves extracting the template literal contents as CSS rules, replacing dynamic interpolations with CSS custom properties, and updating component JSX to use className strings instead of the styled wrapper. This tool automates the extraction and class-name derivation step.

The converter handles: styled.tag`...`, styled(Component)`...`, css`...`, nested & selectors (expanded to flat rules), and simple prop interpolations mapped to CSS variable comments. Complex runtime logic (conditionals, theme lookups) requires manual replacement — the tool marks these with a comment for review.

Common use cases

  • React Server Components migration — extract styles from runtime CSS-in-JS to static CSS files, enabling use of RSC without styled-components runtime incompatibility.
  • Bundle size reduction — remove styled-components or Emotion from the bundle entirely and replace with a single CSS file, saving 12–15 kB gzipped.
  • CSS Modules adoption — convert each styled component to a .module.css file with the same class names, maintaining the scoping benefit without the runtime cost.
  • Design system audit — extract all CSS declarations from styled-components into a readable stylesheet to audit token usage, duplicates, and inconsistencies.
  • Performance profiling — generate static CSS to benchmark render performance against the CSS-in-JS version and quantify the runtime overhead.

Frequently asked questions

Can this tool handle all styled-components patterns?
It handles the most common patterns: styled.tag``, styled(Component)``, css``, nested & selectors, and static interpolations. Complex patterns — component.attrs(), keyframes helper, ThemeProvider injections, and JavaScript conditionals inside template literals — are marked with a comment for manual review.

What happens to ${props => props.color} interpolations?
The tool converts them to a CSS custom property reference comment: /* var(--color) — was ${props => props.color} */. You then add the custom property to your component's inline style or a parent element and reference it in the CSS.

How are class names derived?
From the const variable name. const PrimaryButton = styled.button`` becomes .PrimaryButton { ... }. If the variable is unnamed (default export), the tag name is used as a fallback.

Does the output work with CSS Modules?
Yes — rename the output file to Component.module.css and import it as styles. Change className="PrimaryButton" to className={styles.PrimaryButton}. The class names match because they come from the variable names.

Is Emotion output the same as styled-components output?
The template literal syntax is identical for the basic patterns. Both styled.button`` (Emotion) and styled.button`` (styled-components) produce the same output. css`` helper blocks are extracted with a generic .CSSBlock class name.