When to Avoid Code Splitting in React

While code splitting is a highly recommended optimization technique for reducing initial bundle sizes in React applications, it is not always the correct approach. Implementing code splitting indiscriminately can lead to increased network overhead, poor user experiences, and unnecessary architectural complexity. This article details the specific scenarios where you should avoid code splitting in React and keep your code bundled together.

1. Small Bundle Sizes

If your entire React application’s bundle size is already small (under 100KB to 150KB gzipped), code splitting is unnecessary. The overhead of setting up dynamic imports, managing React Suspense boundaries, and making additional HTTP requests to fetch separate chunks outweighs any marginal load-time benefits. In small apps, loading a single, slightly larger file is faster and more efficient than making multiple round-trips to the server.

2. Critical Above-the-Fold Content

Any component that is essential for the initial paint of your application should never be code-split. Dynamic loading introduces a delay while the browser fetches, parses, and executes the JavaScript chunk. If you code-split critical above-the-fold elements—such as your main navigation, hero sections, or primary header—users will experience visible layout shifts (Cumulative Layout Shift) and loading spinners, which negatively impacts core web vitals and user perception of speed.

3. Frequently Accessed and High-Interactive Elements

Components that users interact with immediately and frequently should remain in the main bundle. For example, if you code-split a dropdown menu, a modal, or tab content that users expect to open instantly, the first click will trigger a network request. This introduces a noticeable lag or “jank” in the user interface. High-frequency interactive elements must be pre-loaded so they respond instantly to user input.

4. Nested Dependencies Creating Network Waterfalls

Avoid code splitting deeply nested components within your application tree. When you chain multiple dynamic imports (e.g., Component A dynamically loads Component B, which then dynamically loads Component C), you create a network waterfall. The browser must wait to download and execute Component A before it even discovers it needs to download Component B. This leads to a staggered, slow-loading interface that frustrates users.

5. Server-Side Rendering (SSR) Without Proper Tooling

If you are using Server-Side Rendering (SSR) without frameworks like Next.js that handle routing and splitting out-of-the-box, manual code splitting can be highly problematic. Standard React dynamic imports (React.lazy) can cause hydration mismatches on the client side if the chunks are not preloaded before hydration begins. Unless you are using advanced setups like loadable-components or React’s modern server components, manual code splitting in custom SSR setups should be avoided to prevent broken UI hydration.