The State of CSS-in-JS in 2026
CSS-in-JS isn’t going away — but the way developers use it has fundamentally changed. If you’re building with React, Next.js, or a component-based design system today, the question isn’t whether CSS-in-JS is dead. It’s whether the runtime model still makes sense for your architecture.
Here’s a clear-eyed look at where things stand.
Key Takeaways
- The CSS-in-JS ecosystem has split into two camps: runtime libraries (styled-components, Emotion) and zero-runtime tools (vanilla-extract, Panda CSS, StyleX).
- React Server Components and streaming SSR made runtime CSS-in-JS significantly more complex in modern Next.js architectures.
- Zero-runtime tools extract styles at build time, eliminating most runtime styling overhead and hydration complexity.
- Runtime CSS-in-JS still fits client-only apps, React Native, and codebases requiring true runtime theming.
- For new React or Next.js projects in 2026 — especially RSC-heavy ones — zero-runtime styling is increasingly the default choice.
The Core Split: Runtime vs. Zero-Runtime CSS-in-JS
The CSS-in-JS ecosystem has divided into two distinct camps.
Runtime CSS-in-JS — libraries like styled-components and Emotion — generate and inject styles via JavaScript during render. This works well in client-rendered apps, but it comes with real costs: additional JavaScript bundle weight, runtime style insertion, and hydration complexity in server-rendered environments.
Zero-runtime CSS-in-JS — tools like vanilla-extract, Panda CSS, and StyleX — extract styles at build time and output static CSS files. No JavaScript runs at render time for styling. The browser gets a plain stylesheet.
The performance difference matters most at scale and under constrained conditions. On mid-range mobile devices with slower connections, runtime style insertion can increase main-thread work during hydration. Zero-runtime tools largely sidestep this entirely.
How React Server Components Changed the Equation
React Server Components (RSC) and the Next.js App Router made the runtime model significantly more complicated, not just slower.
Runtime CSS-in-JS depends on collecting and inserting styles during rendering. Server Components run on the server and don’t support client-side runtime behavior directly. The result: libraries like styled-components and Emotion typically require Client Component boundaries, style registries, or SSR-specific integration layers when used with the App Router.
This doesn’t make runtime CSS-in-JS unusable in modern Next.js applications, but it does reduce some of the architectural simplicity and performance benefits that RSC was designed to provide. The official Next.js CSS-in-JS documentation explicitly calls out these limitations and integration requirements.
React 18’s streaming SSR compounds the issue. Runtime style insertion can interact awkwardly with streamed HTML chunks, increasing the risk of flashes of unstyled content and hydration edge cases.
Zero-runtime CSS-in-JS has no such limitation. Styles are already compiled into static CSS files before the server renders anything.
React 19 also introduced improved native handling for stylesheet precedence and deduplication via the <style> component API, reducing some historical pain points around style management — though it doesn’t make runtime CSS-in-JS inherently RSC-native.
Where Each Approach Fits in 2026
| Approach | RSC Compatible | Runtime Styling Cost | Best For |
|---|---|---|---|
| styled-components | ✅ Yes, v6.3+ | Yes | Existing styled-components apps, client-heavy apps, RSC with constraints |
| Emotion | ⚠️ Partial | Yes | MUI-based design systems, Client Components |
| vanilla-extract | ✅ Yes | None | TypeScript-first design systems |
| Panda CSS | ✅ Yes | None | CSS-in-JS DX with RSC support |
| StyleX | ✅ Yes | None | Large-scale atomic CSS |
| CSS Modules | ✅ Yes | None | Simple scoped styles, any team size |
| Tailwind CSS | ✅ Yes | None | Utility-first, rapid development |
Styled-components remains widely deployed — it’s in millions of production codebases and isn’t going anywhere soon. But it entered maintenance mode in 2025, and many new React Server Components-heavy projects now evaluate zero-runtime alternatives first.
Vanilla-extract offers some of the strongest TypeScript integration in the styling ecosystem. You author styles in .css.ts files with full type safety, design token enforcement at compile time, and zero runtime overhead.
Panda CSS is the closest spiritual successor to traditional CSS-in-JS. The authoring experience feels familiar, while the output is static atomic CSS.
Discover how at OpenReplay.com.
When Runtime CSS-in-JS Still Makes Sense
Don’t migrate for the sake of it. Runtime CSS-in-JS is still appropriate when:
- Your app is client-rendered only with no SSR or RSC
- You’re maintaining an existing Emotion or styled-components codebase that works and isn’t hitting performance ceilings
- You need true runtime theming — styles that change based on user data fetched after page load
- You’re working with React Native, where the StyleSheet model is idiomatic
The cost of migrating a large, stable codebase rarely justifies the performance gains unless you’re actively adopting RSC or experiencing measurable rendering bottlenecks.
Conclusion
The CSS-in-JS debate has matured past tribalism. Runtime libraries aren’t failures — they solved real problems when they were built. Zero-runtime tools solve many of the tradeoffs that runtime libraries introduced.
If you’re starting a new React or Next.js project in 2026, the safer default is increasingly static styling: CSS Modules for simplicity, Tailwind for utility-first development, and vanilla-extract or Panda CSS if you want CSS-in-JS ergonomics without the runtime cost.
If you’re maintaining an existing codebase, migrate incrementally and only when there’s a concrete reason — not because the ecosystem moved on.
FAQs
No, styled-components is not deprecated, but it has entered maintenance mode. The library still receives updates and remains stable for production use. However, it has known limitations with React Server Components, and many new projects in 2026 evaluate zero-runtime alternatives like vanilla-extract or Panda CSS first.
Yes, but integration is more complex than with static CSS approaches. In practice, these libraries typically require Client Component boundaries, style registries, or SSR-specific setup when used with the App Router. Both libraries can work in modern Next.js applications, but zero-runtime tools generally fit the React Server Components model more naturally.
CSS Modules use plain CSS files with locally scoped class names, requiring no JavaScript syntax for styles. Zero-runtime CSS-in-JS like vanilla-extract lets you author styles in TypeScript or JavaScript, then extracts them at build time. Both produce static CSS, but zero-runtime tools offer type safety and programmatic theming that CSS Modules cannot match.
Not unless you have a concrete reason. Migration is justified if you're adopting React Server Components, hitting measurable performance bottlenecks, or undertaking a major rewrite anyway. For stable, client-rendered applications that perform well, the engineering cost of migration rarely pays off in proportional gains.
Truly understand users experience
See every user interaction, feel every frustration and track all hesitations with OpenReplay — the open-source digital experience platform. It can be self-hosted in minutes, giving you complete control over your customer data. . Check our GitHub repo and join the thousands of developers in our community..
