Since you're using the ES6 import syntax you may use the same syntax to import your stylesheet

import './App.css'

Also, you can wrap your class with :global to switch to the global scope (this mean CSS Module won't modulify it, eg: adding a random id next to it)

:global(.myclass) {
  background-color: red;
}
Answer from felixyadomi on Stack Overflow
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Every-layout
every-layout.dev › rudiments › global-and-local-styling
Global and local styling: Every Layout
When people talk about the global nature of CSS, they can mean one of a few different things. They may be referring to rules on the :root or <body> elements that are inherited globally (with just a few exceptions). :root { /* ↓ Now (almost) all elements display a sans-serif font */ font-family: sans-serif; } Alternatively, they may mean using the unqualified * selector to style all elements directly.
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Gatsby
gatsbyjs.com › documentation › how-to guides › styling › standard css
Standard Styling with Global CSS Files | Gatsby
Traditionally, websites are styled using global CSS files. Globally-scoped CSS rules are declared in external .css stylesheets, and CSS…
Discussions

reactjs - How to apply global styles with CSS modules in a react app? - Stack Overflow
I'm currently using CSS Modules with React for my styling. So each of my components is importing in it's component specific css file, like so: import React from 'react'; import styles from './App.... More on stackoverflow.com
🌐 stackoverflow.com
Do you have your own global.css file?
There are a ton of CSS philosophies, like BEM , Cube , utility classes , etc. Try out some approaches and stick with what feels good, also things might change when you work with a larger team. More on reddit.com
🌐 r/webdev
19
4
October 16, 2024
TUTORIAL – Add Global Styles in CSS
In WeWeb, you can add global styles in CSS. Here’s how: Upload your CSS stylesheet to WeWeb Go to your project Settings > File > Upload new file and uploading your CSS stylesheet Link your CSS stylesheet in the head of… More on community.weweb.io
🌐 community.weweb.io
0
1
January 27, 2022
[feature request] use subreddit style with global style setting disabled

I was just wondering what to do with the rest of my afternoon, too.

More on reddit.com
🌐 r/Enhancement
5
20
June 14, 2015
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CSS-Tricks
css-tricks.com › defining-global-styles-in-wordpress
Defining Global Styles | CSS-Tricks
March 1, 2023 - We already covered top-level styles in Part 2. By “top-level” we mean styles that are applied globally on the root element (<html>) as well as the <body>. These styles are “top-level” in the sense they are inherited by everything in the theme by default. The classic example in CSS is setting a default font size on the <body> element:
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Cwicly
docs.cwicly.com › global-styles › global-styles
Global Styles | Documentation
September 11, 2023 - Global Styles are CSS styles that are applied to elements throughout the entire website, rather than being applied only to specific elements on individual pages.
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meyerweb
meyerweb.com › eric › articles › webrev › 199805.html
Creating a Global Style Sheet
None of it is, actually, since the point of style sheets is that they let you define appearance without disturbing the document's structure. but never mind that now. Now that it's been entered into your text editor, you'll want to save the above text to a file called general.css.
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Next.js
nextjs.org › learn › pages-router › assets-metadata-css-global-styles
Pages Router: Global Styles | Next.js
The reason that global CSS can't be imported outside of pages/_app.js is that global CSS affects all elements on the page. If you were to navigate from the homepage to the /posts/first-post page, global styles from the homepage would affect /posts/first-post unintentionally.
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Next.js
nextjs.org › learn-pages-router › basics › assets-metadata-css › global-styles
Global Styles - Assets, Metadata, and CSS
The reason that global CSS can't be imported outside of pages/_app.js is that global CSS affects all elements on the page. If you were to navigate from the homepage to the /posts/first-post page, global styles from the homepage would affect /posts/first-post unintentionally.
Find elsewhere
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GeeksforGeeks
geeksforgeeks.org › css › foundation-css-global-styles
Foundation CSS Global Styles - GeeksforGeeks
July 23, 2025 - Global Style Colors: The default color palette made available for use by Foundation CSS.
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Scalablecss
scalablecss.com › styled-components-global-styles
How to Create Global Styles with Styled Components - Scalable CSS
June 2, 2020 - Learn how to leverage the createGlobalStyle function and set global styles with Styled Components
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Sarasoueidan
sarasoueidan.com › blog › style-settings-with-css-variables
Global and Component Style Settings with CSS Variables
June 1, 2020 - Over the last few months, I’ve started approaching the way I organize and manage my CSS differently… · Today, at the beginning of each project, I create a _settings.scss stylesheet. This stylesheet contains the global settings for the project.
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Reddit
reddit.com › r/webdev › do you have your own global.css file?
r/webdev on Reddit: Do you have your own global.css file?
October 16, 2024 -

As someone who's learning about Web Dev (with React), I just noticed how handy a global.css file is for keeping the same look across all of the pages and components.
I'd establish a palette of at least 5 matching colors to use. I'd set responsive font sizes for different devices. I could also set how buttons should look like and behave. And so on...

Question is, is this a common practice? Is that how you or your company keep the styles unified for every single project's frontend?

Example:

.global-title {
  font-size: 0.8rem;
  font-weight: 600;
}
/* Medium screens */
@media (min-width: 768px) {
  .global-title {
    font-size: 1rem; 
  }
}
/* Large screens  */
@media (min-width: 1024px) {
  .global-title {
    font-size: 1.2rem;  
  }
}
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Astro
docs.astro.build › en › guides › styling
Styles and CSS - Astro Docs
While <style> tags are scoped and only apply to the component that declares them, imported CSS can “leak”. Importing a component applies any CSS it imports, even if the component is never used: ... This header will be purple! ... A common pattern in Astro is to import global CSS inside a Layout component.
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WordPress
make.wordpress.org › core › 2023 › 03 › 06 › custom-css-for-global-styles-and-per-block
Custom CSS for global styles and per block – Make WordPress Core
March 6, 2023 - WordPress 6.2 provides theme authors and end-user with methods to add global and pre block custom CSS.
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WeWeb Community
community.weweb.io › tutorials
TUTORIAL – Add Global Styles in CSS - Tutorials - WeWeb Community
January 27, 2022 - In WeWeb, you can add global styles in CSS. Here’s how: Upload your CSS stylesheet to WeWeb Go to your project Settings > File > Upload new file and uploading your CSS stylesheet Link your CSS stylesheet in the head of…
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W3Schools
w3schools.com › tags › att_global_style.asp
HTML Global style Attribute
The style attribute can be used on any HTML element (it will validate on any HTML element. However, it is not necessarily useful). ... If you want to use W3Schools services as an educational institution, team or enterprise, send us an e-mail: sales@w3schools.com · If you want to report an error, or if you want to make a suggestion, send us an e-mail: help@w3schools.com · HTML Tutorial CSS Tutorial JavaScript Tutorial How To Tutorial SQL Tutorial Python Tutorial W3.CSS Tutorial Bootstrap Tutorial PHP Tutorial Java Tutorial C++ Tutorial jQuery Tutorial
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Documentation
docs.generateblocks.com › home › articles › global styles overview
Global Styles Overview - Documentation (v1)
February 29, 2024 - Global Styles are new in GenerateBlocks Pro 1.7.0, which is currently in public testing. They require GenerateBlocks 1.9.0 (also in public testing). Global styles consist of a collection of CSS classes that are loaded globally across your entire website. You can create a class, add styles to ...
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Theme-ui
theme-ui.com › guides › global-styles
Global Styles – Theme UI
Global Styles · TypeScript · Recipes · Migrating · Theme UI offers a Global component (that wraps Emotion’s) for adding global CSS with theme-based values. By default (or, unless the useRootStyles configuration optionis disabled), the ThemeUIProvider component will apply styles in theme.styles.root to the <html> element.
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Emotion
emotion.sh › docs › globals
Emotion – Global Styles
Sometimes you might want to insert global css like resets or font faces. You can use the Global component to do this. It accepts a styles prop which accepts the same values as the css prop except it inserts styles globally.
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Next.js
nextjs.org › docs › app › getting-started › css
Getting Started: CSS | Next.js
2 days ago - Create a app/global.css file and import it in the root layout to apply the styles to every route in your application: