How to remove redundant CSS styles

In web development, CSS is an indispensable part. However, due to the continuous code modification and update, we will inevitably leave some redundant style code in the CSS file. Although these codes may seem harmless, they actually affect the performance and loading speed of your web pages. Therefore, removing redundant CSS is a very important task.

1. The impact of clearing redundant CSS on web page performance

1. Loading speed slows down

Excessive CSS code will make the code volume of the web page become larger Large, which results in slower loading of web pages. When the browser downloads HTML, CSS, JavaScript and other files, they do so in an order. If the CSS file size is too large, it will prevent other files from downloading, thus slowing down the loading speed of the web page.

2. Rendering speed slows down

As web pages continue to grow, the browser needs to work harder to render the corresponding content. If there are too many CSS codes, the browser will take longer to process them, which will slow down the rendering speed of the web page. This is why sometimes it takes a long time to open a simple web page.

3. Browser handling of redundant CSS

The browser will find redundant CSS in the code, but they will still be parsed. This is because browsers only know how to parse HTML, CSS, and JavaScript. So even if you have 50 redundant CSS at the beginning of a web page, you have to wait until they are all downloaded and parsed before rendering can begin. This will significantly slow down the loading speed of web pages.

2. How to clear redundant CSS

The core idea of ​​clearing redundant CSS is to reduce the amount of code on the web page. Here are several ways to remove excess CSS:

1. Manually remove excess CSS

Manually removing excess CSS is the most basic method. We can read the code line by line in the CSS file and analyze whether each class is necessary. If the class is not used, it can be deleted.

2. Use online tools to delete redundant CSS

There are some online tools that can delete unused classes in CSS files. These tools parse CSS files through a CSS parser and find unused classes in the file. We can delete unused classes by dragging CSS files into these tools and clicking the delete button.

3. Use build tools to remove redundant CSS

By using build tools, we can automatically remove unused classes. Build tools compile a website's source code into a compressed version. During the compilation process, the build tool will parse the CSS file through the CSS parser and find unused classes. This will automatically delete unused classes, thus reducing the amount of code.

3. A simple case

Suppose there is a CSS file that contains the following class:

.page-title {
    font-size: 28px;
    font-weight: bold;
    color: #333;
}

.content-main {
    font-size: 16px;
    color: #666;
}

.content-sidebar {
    font-size: 14px;
    color: #999;
}

.footer {
    font-size: 12px;
    color: #999;
}

If we only use .page- title and .content-main classes, then the other two classes are redundant. We can remove them manually from CSS files or we can use online tools or build tools to remove them automatically.

4. Conclusion

It is very important to remove redundant CSS, which can greatly improve the loading and rendering speed of web pages. We can reduce the size of CSS files and keep the code concise and readable by manual removal, using online tools or build tools. When coding CSS, be sure to pay attention to which classes are necessary and which are redundant, and avoid over-writing CSS code.

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