Fixing Initial Flash of Unstyled Content (FOUC) in Angular Component Styles

Описание: Learn why Angular component styles may not load immediately on navigation and how to prevent the flash of unstyled content with simple optimizations and workarounds.
---
This video is based on the question https://stackoverflow.com/q/79510171/ asked by the user 'Gerard' ( https://stackoverflow.com/u/29004376/ ) and on the answer https://stackoverflow.com/a/79510601/ provided by the user 'Naren Murali' ( https://stackoverflow.com/u/5924562/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: My page does not load the styles correctly when accessing one of its links in Angular

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to drop me a comment under this video.
---
Understanding the Problem: Flash of Unstyled Content (FOUC) in Angular

When navigating to routes in an Angular application, you might briefly see components like sidebars or other UI parts rendered without CSS styles. This effect, often called a Flash of Unstyled Content (FOUC), happens because Angular lazy-loads component styles and they take a moment to apply after the HTML is rendered.

Why does this happen?

Component-scoped styles: When each Angular component includes its own styles, these styles are encapsulated and loaded only when the component is rendered.

Network delays: Slow internet or large CSS files increase the time before styles are applied.

Development mode differences: This issue often appears more prominently in development servers where file bundling and compression are not fully optimized.

Effective Solutions to Prevent FOUC

1. Optimize Asset Delivery

Enable compression like gzip or brotli on your web server.

Compression drastically reduces CSS payload sizes and speeds up style delivery.

2. Use a Loading Indicator (Practical Workaround)

Display a loader or spinner while component styles are still loading.

For example, in your root component, show a simple overlay for 1 second, enough time for styles to be fetched and applied:

[[See Video to Reveal this Text or Code Snippet]]

[[See Video to Reveal this Text or Code Snippet]]

This ensures users never see the unstyled content.

3. Consider Global Styles Where Appropriate

If feasible, use global styles or shared CSS files for common UI elements like sidebars.

This avoids repeated style loading per component and reduces visual inconsistencies.

Summary

While Angular's component-based style system improves encapsulation, it can cause momentary style flashes on route changes. To address this:

Optimize your server with compression (gzip/brotli).

Show a loader briefly on app startup or route changes.

Use global styles cautiously to minimize style loading delays.

These steps significantly improve perceived performance and user experience.