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Yan Levin
Yan Levin

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Why CSS-in-JS Doesn't Solve Problems

CSS-in-JS has gained significant traction in the web development community over the past few years. Proponents argue that it offers a modular, scoped, and dynamic way to style components, especially within the context of JavaScript-heavy frameworks like React. However, despite its popularity, CSS-in-JS introduces a range of challenges and complexities that suggest it may not be the silver bullet solution for managing styles in web applications. Here, we'll explore some of the fundamental reasons why CSS-in-JS doesn't necessarily solve the problems it sets out to address.

Performance Overheads

One of the primary criticisms of CSS-in-JS is the performance overhead it introduces. Traditional CSS is parsed and applied by the browser very efficiently. CSS-in-JS, however, requires styles to be generated and injected into the DOM at runtime, which can lead to significant performance hits, particularly in large applications. This runtime cost includes parsing JavaScript, generating styles, and manipulating the DOM, all of which can contribute to slower page load times and a less responsive user experience.

Increased Bundle Size

With CSS-in-JS, styles are typically included in the JavaScript bundle. This means that every component with its associated styles contributes to the overall size of the JavaScript bundle. As a result, applications can become bloated, leading to longer download and parse times. This is a stark contrast to traditional CSS, which can be minified and cached separately, reducing the amount of data transferred and improving overall load times.

Complexity and Learning Curve

CSS-in-JS introduces a new syntax and set of concepts that developers need to learn. While traditional CSS has a well-established and straightforward syntax, CSS-in-JS solutions often require familiarity with JavaScript template literals, tagged templates, and sometimes even CSS preprocessors like Sass. This added complexity can steepen the learning curve for new developers and increase the cognitive load for experienced developers, making the development process more cumbersome.

Poor Separation of Concerns

One of the foundational principles of web development is the separation of concerns: HTML for structure, CSS for presentation, and JavaScript for behavior. CSS-in-JS blurs these lines by embedding styles directly within JavaScript files. This can lead to harder-to-maintain codebases, as styles are no longer isolated from the logic and structure of the application. When styling rules are mixed with component logic, it can become more challenging to manage and debug issues, especially in larger applications.

Inconsistent Styling Approaches

CSS-in-JS can lead to inconsistent styling approaches within a codebase. Different libraries and frameworks offer various ways to implement CSS-in-JS, each with its own syntax and conventions. This inconsistency can result in a fragmented codebase where styles are applied in multiple ways, making it harder to enforce a unified design system. Traditional CSS, especially when combined with methodologies like BEM (Block, Element, Modifier) or utility-first CSS frameworks, provides a more consistent and predictable approach to styling.

Lack of Tooling and Ecosystem Support

While CSS-in-JS solutions have matured, they still lack the extensive tooling and ecosystem support available for traditional CSS. Tools like PostCSS, Autoprefixer, and CSS linting utilities have been developed and refined over years to enhance the CSS development workflow. Although some CSS-in-JS libraries offer plugins and integrations, they often fall short of the comprehensive support and flexibility provided by the broader CSS ecosystem.


While CSS-in-JS offers some compelling features, such as scoped styles and dynamic theming, it introduces a range of challenges that can negate its benefits. Performance overheads, increased bundle sizes, added complexity, poor separation of concerns, inconsistent styling approaches, and limited tooling support are significant drawbacks that make CSS-in-JS less appealing for many projects.

In many cases, traditional CSS, possibly enhanced with modern methodologies like BEM, utility-first frameworks like Tailwind CSS, or preprocessors like Sass, can provide a more efficient, maintainable, and performant solution. Developers should carefully weigh the pros and cons of CSS-in-JS and consider their specific project requirements before adopting this approach.

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