Is the CSS Star Selector a Performance Bottleneck?

CSS Star Selector: A Performance Pitfall

Is the CSS star selector harmful? Yes, it can be detrimental to page rendering performance.

How the Star Selector Affects Performance

As Steve Souders, a renowned performance expert, explains, the browser evaluates CSS selectors right to left. When using the star selector, "*", the browser must check it against every element on the page. This can be highly inefficient, especially for complex documents with numerous elements.

Caveats of Using the Star Selector

Aside from performance implications, using the star selector has several caveats:

• Lack of specificity: The star selector has zero specificity, which means it can be easily overridden by other more specific selectors in the stylesheet.
• Poor maintainability: Star selectors make it harder to manage CSS rules because they can apply to multiple elements unintentionally.
• Potential security risks: In some rare cases, star selectors can lead to unexpected security vulnerabilities by allowing unauthorized access to page elements.

Example

Consider the following CSS code:

* {
  margin:0;
  padding:0;
}

This code will set the margins and paddings of all elements on the page to 0, which can be an excessive and undesired behavior. A better approach is to use more specific selectors to target only the elements that need those styles.

Conclusion

While the star selector may seem like a convenient shorthand, it is crucial to use it with caution. By understanding its performance implications and caveats, developers can make informed decisions and optimize their CSS stylesheets for better page rendering and maintainability.

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