Does '!important' Hurt Website Performance?

!important and Performance: A Discussion

The use of "!important" in CSS has been a subject of debate among web developers, igniting concerns over its impact on page performance. This article explores the topic, examining whether "!important" negatively affects performance, as some believe.

Investigating Performance Implications

According to an analysis of the Firefox CSS parser, the presence of "!important" does not appear to have a discernible effect on performance. The parser checks for "!important" when overwriting CSS rules, marking the affected rules efficiently without significant additional cost.

Maintainability vs. Performance

While "!important" does not pose a threat to performance, it can hinder maintainability. The cascading nature of CSS becomes less reliable when "!important" is used excessively, potentially leading to unintended consequences and making it challenging to troubleshoot code.

Conclusion

The analysis of the Firefox CSS parser suggests that the use of "!important" has minimal impact on performance. However, its potential for reducing maintainability remains a valid concern. Designers must weigh the trade-offs carefully, considering the specific context and the importance of maintaining a clean and manageable codebase.

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