px vs. rem in CSS: Which Unit Should I Use for Consistent Layouts?

CSS Unit of Measurement: px vs. rem

Deciding between px and rem for CSS unit of measurement can be perplexing due to conflicting opinions. However, it's crucial to understand the following:

px

• It's relative to the reference pixel, not physical display pixels.
• Browsers rescale px to match the reference pixel size, regardless of display DPI.

em

• Relative to the parent element, causing sizes to compound.
• This can make element sizes unpredictable when nested deeply.

rem

• Relative only to the root HTML element.
• Widely supported and addresses the compounding issue of em.

Recommendation

Despite the arguments for relative units, modern browsers' zoom functionality effectively scales all elements, making relative units largely irrelevant.

Conclusion

For consistency and ease of development, it's recommended to use px for all CSS unit measurements. This ensures your layout remains consistent regardless of user-adjusted font sizes. While relative units may be necessary for older browsers like IE6, px is the preferred option for modern web development.

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