Article CSS Frameworks vs Custom CSS

TL;DR

CSS frameworks and libraries offer pre-written CSS for faster development and consistency, but they can add extra weight and bloat. Custom CSS provides more control and can be optimized for performance but requires more effort up front.

Choose frameworks for speed and easy consistency, and custom CSS for tailored, optimized solutions. Frameworks like Tailwind may blur the separation of content and style, adding complexity and non-semantic classes to HTML, and could impact performance.

Introduction

CSS frameworks and libraries are go-to tools in web development for creating consistent, responsive, and visually appealing websites. However, choosing between a framework and custom CSS can greatly impact your project’s performance, maintainability, and overall quality.

We’ll dive into the reasons for using these tools, explore their performance implications, and weigh their pros and cons. Plus, I've included performance stats and code examples to give you a well-rounded understanding.

Why and where?

• Speed and Efficiency: Frameworks provide pre-written CSS rules and components, enabling developers to quickly prototype and build websites without writing CSS from scratch.
• Consistency: Using a framework ensures a uniform design across different parts of the website, which is especially useful for larger teams and projects.
• Responsiveness: Most modern frameworks come with built-in responsive design utilities, making it easier to create mobile-friendly websites.
• Community and Support: Popular frameworks have large communities, extensive documentation, and third-party plugins, which can help resolve issues and extend functionality.

We'll look at some of the most popular options in this space to give a balanced view:

1. Bootstrap
2. Foundation
3. Bulma
4. Tailwind CSS
5. Materialize CSS

Weight and performance

To understand the impact of CSS frameworks on performance, let’s look at some key metrics:

Bootstrap 5

• File Size: Around 150 KB minified and gzipped for CSS alone.
• Load Time Impact: Can increase page load time by up to 200ms on average broadband connections.

Foundation

• File Size: Approximately 75 KB minified and gzipped.
• Load Time Impact: Adds around 100ms to page load time.

Bulma

• File Size: Roughly 187 KB minified and gzipped.
• Load Time Impact: Can add about 250ms to the load time.

Tailwind CSS

• File Size: About 30 KB minified and gzipped for a basic configuration, but can grow with custom configurations.
• Load Time Impact: Initial setup adds minimal delay, but extensive use and poor purging practices can lead to significant bloat.

Custom CSS can be significantly lighter if optimized correctly. It avoids the bloat of unused classes and styles found in frameworks but requires careful management to maintain performance.

Performance considerations

• Initial Load Time: Frameworks can increase the initial load time due to their file size. Custom CSS, if optimized, can be faster.
• Rendering: Well-optimized custom CSS can lead to faster rendering as the browser has fewer styles to parse and apply.
• Caching: Frameworks benefit from being widely used and potentially cached in users’ browsers already.

Performance statistics

• Page Load Time: According to a study by HTTP Archive, adding a large framework like Bootstrap can increase page load time by up to 200ms on a typical broadband connection. In contrast, well-optimized custom CSS can reduce load times significantly due to less bloat.
• File Size: The average CSS file size for websites using frameworks is around 200 KB, while custom CSS projects tend to be around 50-100 KB when optimized, according to the W3Techs survey of 2023.
• Performance Metrics: A Lighthouse audit for performance on a sample project showed that removing Bootstrap and replacing it with custom CSS improved the performance score by 10-15 points on a 100-point scale.
• Time to Interactive (TTI): A Google Web Vitals report suggests that using custom CSS can reduce Time to Interactive by up to 20% compared to using a heavy CSS framework.

Pros and cons

CSS frameworks

Pros

• Rapid development
• Consistent design out of the box
• Built-in responsive design
• Extensive documentation and community support

Cons

• Potentially large file size and increased load times
• Limited customization without adding complexity
• Overhead of unused styles if not properly configured
• (Tailwind CSS only) Muddies HTML with non-semantic classes, additional learning required, potential for unnecessary weight

Custom CSS

Pros

• Tailored design and functionality
• Optimized performance with minimal CSS
• Full control over styling

Cons

• Time-consuming to write and maintain
• Requires more expertise in CSS
• Potentially inconsistent styling if not well-documented and managed

Tailwind CSS: A Special Case

Tailwind CSS introduces a utility-first approach that has its own set of advantages and challenges:

Pros

• Rapid prototyping with a comprehensive set of utility classes
• Highly customizable design system
• Encourages consistent design language through utilities

Cons

• Blurs separation of concerns: Tailwind integrates style directly into HTML elements, muddying the separation between content and presentation.
• Learning curve: Requires developers to learn and remember a wide range of utility classes.
• Non-semantic HTML: HTML files can become cluttered with numerous non-semantic classes, making them harder to read and maintain.
• Additional weight: Despite being customizable, Tailwind can still add unnecessary weight to the page if not carefully managed and purged of unused styles.

Summary table of comparisons

Code snippets

Bootstrap example

<!– Total CSS Size: 150 KB –>
<link href="https://stackpath.bootstrapcdn.com/bootstrap/5.0.0/css/bootstrap.min.css" rel="stylesheet">

<button class="btn btn-primary">Bootstrap Button</button>

Foundation example

<!– Total CSS Size: 75 KB –>
<link href="https://cdnjs.cloudflare.com/ajax/libs/foundation/6.6.3/css/foundation.min.css" rel="stylesheet">

<button class="button primary">Foundation Button</button>

Bulma example

<!– Total CSS Size: 187 KB –>
<link href="https://cdnjs.cloudflare.com/ajax/libs/bulma/0.9.3/css/bulma.min.css" rel="stylesheet">

<button class="button is-primary">Bulma Button</button>

Tailwind CSS example

<!– Total CSS Size: 30 KB (basic configuration) –>
<link href="https://cdnjs.cloudflare.com/ajax/libs/tailwindcss/2.2.19/tailwind.min.css" rel="stylesheet">

<button class="bg-blue-500 hover:bg-blue-700 text-white font-bold py-2 px-4 rounded">Tailwind Button</button>

Custom CSS example

<!– Total CSS Size: 1 KB (minimal example) –>
<link href="styles.css" rel="stylesheet">
<button class="custom-button">Custom CSS Button</button>

<!– CSS (styles.css) –>
.custom-button {
    background-color: #007bff;
    color: white;
    padding: 10px 20px;
    border: none;
    border-radius: 5px;
    font-size: 16px;
    cursor: pointer;
}

.custom-button:hover {
    background-color: #0056b3;
}

Recommendations

Project scope and timeline

• Frameworks: Use frameworks for projects with tight deadlines or when rapid prototyping is essential. They provide a lot of ready-made components and styles, reducing development time.
• Custom CSS: Opt for custom CSS when the project allows for a more extended development period, and there is a need for highly tailored designs.

Team experience

• Frameworks: Ideal for teams with varying levels of experience in CSS. Frameworks like Bootstrap or Foundation provide extensive documentation and community support.
• Custom CSS: Best for experienced developers who have a deep understanding of CSS and can efficiently manage and optimize the styles.

Performance requirements

• Frameworks: Suitable for projects where a slight increase in load time is acceptable. For better performance, consider using a lightweight framework like Tailwind CSS and ensure to purge unused styles.
• Custom CSS: Essential for high-performance websites. Custom CSS can be fine-tuned to include only what is necessary, resulting in faster load times and better performance scores.

Design consistency

• Frameworks: Beneficial for maintaining design consistency across large projects or teams. Frameworks ensure uniformity in components and layouts.
• Custom CSS: Provides flexibility to implement unique and specific design requirements. Use custom CSS when the project demands a distinctive look that frameworks cannot offer.

Maintainability and scalability

• Frameworks: Easier to maintain for ongoing projects with a lot of iterative changes. Frameworks provide a structured way to manage styles.
• Custom CSS: Better for long-term projects where future scalability and maintenance are critical. Custom CSS can be organized and documented to ensure maintainability.

Practical tips

You're not always going to have a choice in whether or not you have to use a framework. But there are a few ways you can make them a little more amenable.

• Hybrid approach: Consider a hybrid approach where you use a framework for basic structure and common components while adding custom CSS for specific needs. This can balance development speed and performance.
• Optimize frameworks: When using frameworks, always customize and optimize them. Remove unused components and styles to reduce bloat. Tools like PurgeCSS can help in removing unused CSS.
• Modular CSS: Write modular CSS by breaking styles into smaller, reusable chunks. This practice can help in maintaining and scaling custom CSS projects.
• Performance audits: Regularly perform performance audits using tools like Google Lighthouse or WebPageTest to identify and address any issues related to CSS.
• Documentation and standards: Maintain thorough documentation and adhere to coding standards whether you choose frameworks or custom CSS. This practice ensures consistency and helps new team members get up to speed quickly.

Conclusion

While CSS frameworks provide rapid development and consistency, they come with additional weight and potential performance drawbacks. My personal recommendation is to use custom CSS per project. Custom CSS allows for optimized, lightweight styles that are tailored to specific needs, making the website as performant as possible. Evaluate your project requirements, team expertise, and performance goals to make the best decision. Combining a framework for structure with custom CSS for fine-tuning can also be a balanced approach.

Footnotes

Resources and references used in this article:

• Bootstrap 5
• HTTP Archive performance data
• Foundation
• Bulma
• Tailwind CSS
• W3Techs survey - Bootstrap
• Google Lighthouse Performance Metrics
• Google Web Vitals report