Angular shadowdom patch

Use this patch at your own risk, it is not maintained by the Angular team and may not work with the latest versions of Angular.

Tested in Angular version 19.x and 20.x but cannot guarantee it will work with future versions.

Compatibility

Version 3 is the most reliable version as it is more robust to class signature changes in Angular patches.

This version	Angular version
3.0.3	> 19.x
2.0.0	20.2.0
1.0.2	19.x - 20.1.x

What this patch does:

Currently, Angular's shadow dom implementation pulls in extra styling from the sharedStylesHost, which can massively add to bloat per component implementation.

This patch removes the sharedStylesHost from the dom_renderer.js shadow dom class, only rendering the styles that are defined in the component itself.

This patch will search your node_modules for the @angular/platform-browser package and patch the dom_renderer.js file to remove the sharedStylesHost.

Why this patch is needed:

Angular's shadow dom implementation is currently not optimized for performance, as it pulls in all styles from the sharedStylesHost, which can lead to unnecessary bloat and performance issues in applications that use shadow dom.

How to use this patch:

Install the npm module.

Add a postinstall script to your package.json:

"scripts": {
"postinstall": "node node_modules/angular-shadowdom-patch",
}

Now when you run npm install, the patch will be applied automatically.

You should see a message in the console indicating that the patch has been applied.

Before

After

Questions

I am still seeing extra styles in my shadow dom components, what should I do?

Sometimes node_modules can be cached, so what I usually do is kill your dev server, delete the @angular/platform-browser directory in node_modules, and then run npm install again.