A CSS framework comprises multiple ready-to-use CSS libraries for developers and web designers. The stylesheets are prepared for everyday tasks in web design, such as the navbar, font, colour, and layout setup. They simplify the job of a UI developer, providing them with tools to create a user interface rather than starting every project from scratch. Stylesheets are supported and expanded by other scripting technologies like JavaScript.

When using a CSS framework, the user must code the HTML with the correct classes, structure, and IDs to create a web page because the CSS stylesheet is complete. The framework already includes built-in classes for common website elements, like a footer.

When are CSS frameworks used?

Front-end developers use CSS frameworks to swiftly implement key user interface elements on websites and applications, such as buttons, styled forms, and adaptable grids.

The most straightforward answer as to why people use frameworks is speed. Frameworks come out of the box with plenty of elements and styles you would otherwise need to build from scratch when developing a website. Many developers and web designers also use frameworks to rapidly prototype new websites or apps before building a custom design system.

Here’s a list of the most useful CSS frameworks of 2023: 

1. Tailwind CSS 

According to the 2023 State of CSS study, “once again, Tailwind CSS stands apart as the one major UI framework that developers are happy to keep using”.

Tailwind is a “utility-first CSS framework” that provides classes enabling users to create custom user interfaces directly within the user's markup. Implementing inline styling is helpful for quickly creating an eye-catching UI without coding any CSS.

Tailwind CSS is one of the most popular utility CSS libraries and offers other significant advantages for web design. In practice, while Tailwind makes reading class attributes at a glance harder, you gain all of that back with how it simplifies the actual maintenance of the styles. Tailwind also eliminates the need for intermediate class names to hook styles onto, which is helpful, especially when an error or code drift makes the class name misleading.

And there's one significant difference between Tailwind classes and inline styles: specificity! Inline styles override CSS class-based styles regardless of source code organisation, leading to extraordinarily frustrating situations when an element requires context-sensitive styling. With Tailwind, it's all classes, just like most handwritten CSS, which makes mixing custom CSS and framework styles predictable.

In short, when prototyping, you can slap together handwritten styles, however, it is convenient. Still, when making complex web applications, Tailwind gracefully works with the exact mechanism for organisation and encapsulation as the rest of the UI: a component.

Companies that use it: 

• OpenAI.com
• Shopify.com 
• Medium
• GitHub’s Primer design system

2. Bootstrap  

Created by Mark Otto and Jacob Thornton at Twitter, Bootstrap is an open-source framework that uses CSS and JavaScript-based interface component templates to encourage uniformity among internal tools. It championed the now-ubiquitous concept of mobile-first and provided the necessary tools for its seamless implementation. Bootstrap facilitated the straightforward adoption of the prevalent mobile-first approach by incorporating a grid system, which discretely divided the screen into columns unseen by the end user.

Developers are no longer compelled to embark on separate projects solely to adjust a website for smaller screen sizes, courtesy of Bootstrap. The design automatically adjusts when incorporating the requisite Bootstrap classes.

Since it's a widely used and tested library, with plenty of contributors and reviewers, there are a lot of practical architecture/design choices that you can learn from if you take the time to read and understand the actual code (and even the issues that lead to them). In addition, it offers some very thorough and relatively straightforward documentation. It's also very extensible and, at the same time, granular.

Companies that use it:

More than half a million projects are using Bootstrap. The most popular include:

• Spotify
• Twitter
• Udemy
• Robinhood
  

3. Materialize CSS 

Materialize is a CSS framework crafted and conceptualised by Google, founded on the principles of Material Design—an innovative design language that seamlessly melds creativity and technology. Google aims to create a design framework that provides a unified user experience across all its products on any platform.

This framework offers default styling that integrates custom components, refined animations, and transitions, ensuring a seamless experience for users. Materialize stands out as a user experience-focused framework that incorporates components and animations designed to provide enhanced feedback to users. Detailed documentation is provided, along with specific code examples, to assist new users in navigating the framework effectively.

Companies that use it:

• GeeksForGeeks
• Mapbox
• JoyPixels
  

4. Foundation

Described on its homepage as “the most advanced responsive front-end framework in the world”, Foundation provides a comprehensive toolkit, including a grid system, HTML, SASS, and CSS user interface elements, templates, and code that encompasses navigation, buttons, typography, forms, and more. Additionally, it offers optional features through extensions for JavaScript. The framework strongly emphasizes mobile devices and proves highly beneficial for the development of substantial web applications requiring a robust design foundation.

Its vast, flexible toolkit is a valuable resource for a wide array of front-end developers, aiding them in finding effective solutions. Foundation presents distinct framework components tailored for both emails and webpages, ready to deploy in their respective domains. Moreover, it features a command-line interface (CLI), which is particularly advantageous for developers engaged in projects involving module bundlers like Webpack.

This framework is designed to give front-end developers total control over their user interfaces. It does not require them to use a specific language or style, which makes it a preferred tool among most. 

Companies that use it:

• Pixar
• Mini Cooper
• Run-DMC
• Barclays Bank

5. Bulma 

Based on Flexbox, Bulma is an open-source, responsive CSS framework known for its exceptional range of built-in functionality, reducing the need for extensive manual CSS coding and ensuring swift response times. It uses tiles to build Metro-style grids that result in sleek and well-organized page layouts. Users can further streamline the process by importing only the specific elements they intend to use.

Bulma stands out as a favourite among developers and designers, thanks to its modular design approach and high level of customisation. Its responsive templates significantly reduce the design workload, offering various components such as dropdown menus, tables, panels, and navigation bars. Bulma also provides interactive tutorials and starter templates. Furthermore, the framework boasts a substantial Stack Overflow community, proving invaluable for obtaining solutions to various issues.

Companies that use it: 

• Infosys
• Fujitsu
• University of California, Berkeley
  

6. Skeleton

Described as a “dead simple, responsive boilerplate” on its homepage, Skeleton stands out as one of the most, if not the most, minimalistic frameworks available. Skeleton is one of the most (if not the most) minimalistic frameworks to exist. With a mere 400 lines of source code, this lightweight tool is designed to generate CDD elements that seamlessly function on both mobile devices and larger screens. Employing a 12-column grid system with a maximum width of 960px, Skeleton accommodates small, medium, and large displays, and a single line of CSS code is all it takes for easy modifications. It incorporates all the essential elements for responsive design, featuring a user-friendly syntax that facilitates quick implementation, making the creation of responsive designs notably straightforward.

This tool is perfect for designers to get started with. You should use Skeleton if you're embarking on a smaller project or just don't feel like you need all the utility of larger frameworks.

Companies that use it: 

• Portale Argo
• The Range
• WikiTree
  

7. Open Props 

This relatively new framework is already in the State of CSS annual survey, which is always a trustworthy indicator of what people enjoy working with.

Open Props is a low-level framework built entirely on CSS variables, meaning it is almost entirely customisable and can be adapted to fit any design system. It uses just-in-time compilation to guarantee that just the CSS variables required for your project are produced, which may aid in improving your application's performance.

Which CSS framework are you starting with?

Using your raw stylesheets in CSS can get out of control quickly, especially when working with a team. Using frameworks such as Tailwind or Open Props enables you to create a custom theme for each site, facilitating the implementation of performant inline styles. Additionally, these frameworks feature a compressed syntax, allowing one to style faster. Why reinvent the wheel if these frameworks offer all the styles you want? Working with frameworks is working smarter and lighter, not harder and heavier. 

At WeAreDevelopers, we’re continually matching season and new developers with the top companies in Europe. CSS is constantly shifting, and working with it might be the best way to stay on top. Check our job boards for opportunities in CSS and many other tech stacks. Good luck!