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[NEXT-1308] Css is imported multiple times and out of order in /app dir

Freshabout 20 hours ago
Mar 14, 20260 views
Confidence Score95%
95%

Problem

Verify canary release [X] I verified that the issue exists in the latest Next.js canary release Provide environment information [code block] Which area(s) of Next.js are affected? (leave empty if unsure) App directory (appDir: true) Link to the code that reproduces this issue or a replay of the bug https://github.com/ssijak/next-css-issue-not-working-simple To Reproduce Just start the app and check the styling on the buttons. Styles are imported multiple times wherever `Button` was used (page and layout) and order is also not deterministic, so it can be imported in different order on different app runs. This is another/same simple repro difference is just that it uses turbo and transpiles the UI lib, I started with that but figured that the issue is happening without it too https://github.com/ssijak/next-css-issue-not-working Describe the Bug \-Same styles are imported multiple times \-Order of imports is not deterministic Screenshot: https://share.cleanshot.com/nq35j7vh Expected Behavior Same styles should be imported once. Starting the app multiple times should not produce different results (ordering of CSS, impacting specificity) Which browser are you using? (if relevant) No response How are you deploying your application? (if relevant) No response* <sub>From SyncLinear.com | NEXT-1308</sub>

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2 Fixes

Canonical Fix
Unverified Fix
New Fix – Awaiting Verification

Fix Multiple CSS Imports and Ordering in Next.js App Directory

Medium Risk

The issue arises from the way Next.js handles CSS imports in the app directory. When components like `Button` are imported in multiple places (e.g., pages and layouts), Next.js may include the same CSS file multiple times, leading to redundancy. Additionally, the order of CSS imports can vary between builds, resulting in inconsistent styling due to differences in specificity.

Awaiting Verification

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  1. 1

    Consolidate CSS Imports

    Ensure that CSS files are imported only once at a higher level in the component hierarchy, such as in the layout or a global styles file.

    javascript
    import '../styles/button.css'; // Import in a common layout or _app.js
  2. 2

    Use CSS Modules

    Refactor the CSS to use CSS Modules, which scope styles to the component and prevent global conflicts. Rename your CSS files to `[name].module.css` and import them directly in the component.

    javascript
    import styles from './Button.module.css'; // Use styles.button for className
  3. 3

    Check for Duplicate Imports

    Review all components for duplicate CSS imports. Remove any redundant imports to ensure each CSS file is imported only once.

    javascript
    // Remove duplicate import statements from Button component
  4. 4

    Ensure Consistent Build Configuration

    Verify that your Next.js configuration is consistent across environments. Check for any differences in the build setup that could affect CSS handling.

    javascript
    // Check next.config.js for any conflicting settings
  5. 5

    Test Across Multiple Runs

    After making changes, start the application multiple times to ensure that the CSS is consistently applied and that there are no duplicate imports.

    bash
    npm run dev // Start the application and check styles

Validation

Confirm the fix by running the application and inspecting the button styles in the browser's developer tools. Ensure that each CSS file is imported only once and that the styles are applied consistently across multiple runs.

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1 low-confidence fix
Unverified Fix
New Fix – Awaiting Verification

Fix Multiple CSS Imports and Ordering in Next.js App Directory

Medium Risk

The issue arises from the way CSS modules are imported in the Next.js app directory. When a component imports CSS files, they may be included multiple times if the same component is used in different places (like pages and layouts). Additionally, the order of these imports can vary between builds due to the dynamic nature of module resolution, leading to inconsistent styling.

Awaiting Verification

Be the first to verify this fix

  1. 1

    Consolidate CSS Imports

    Ensure that all CSS imports for a component are centralized in a single file, preferably in the component's directory. This will prevent multiple imports across different files.

    typescript
    import './Button.css';
  2. 2

    Use a Global CSS File

    If applicable, consider moving shared styles to a global CSS file. This can help in reducing the number of imports and ensuring consistent order.

    css
    @import './styles/global.css';
  3. 3

    Implement CSS Modules

    Utilize CSS Modules for component-specific styles to avoid global namespace collisions and ensure styles are scoped to the component. This can help in managing imports better.

    typescript
    import styles from './Button.module.css';
  4. 4

    Check for Duplicate Imports

    Review the codebase for any duplicate imports of the same CSS file in different components. Remove unnecessary imports to avoid redundancy.

    typescript
    // Remove duplicate imports in components
  5. 5

    Test CSS Order Consistency

    Run the application multiple times and inspect the order of the CSS rules in the browser's developer tools to ensure that the styles are loaded in a consistent order.

    javascript
    console.log('Check CSS order in developer tools');

Validation

Confirm that the styles are now imported only once and that the order of CSS rules remains consistent across multiple runs of the application. Use browser developer tools to inspect the styles applied to the components.

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Environment

Submitted by

AC

Alex Chen

2450 rep

Tags

nextjsreactssrlinear:-nextcss