Web Designer Terence Eden Proposes Replacing Pixels With 'ch' Units

Web design may be shifting from absolute screen measurements to content-centric metrics. Designer Terence Eden has proposed replacing the traditional pixel (px) unit with the character (ch) unit to create layouts driven entirely by typography.

In a blog post titled "Death to px, long live ch!", Eden argues that web widths should be defined by the width of the '0' character rather than fixed pixels. Technically, the 'ch' unit in CSS represents the advance measure of the glyph '0' in an element's specific font. By using this unit, designers tie the layout directly to the font's metrics, ensuring the visual structure of a page scales in harmony with the text.

The Shift from Absolute to Relative

For decades, web design has relied heavily on pixels or relative units such as em and rem. While these tools allow for scaling, they often operate independently of the actual character widths of the chosen typeface. The 'ch' unit is a less commonly utilized CSS tool that specifically targets the zero character, which serves as a reliable proxy for average character width in monospaced fonts and many proportional typefaces.

Why Typography-Driven Layout Matters

This shift moves the industry toward a layout model based on content rather than screen space. The primary goal is to automate the "ideal line length" for readability, which is generally considered to be between 45 and 75 characters.

When widths are set in pixels, a change in font size or a switch to a wider typeface can push a line of text beyond the optimal reading range, forcing the reader's eye to travel too far. By defining a container's width in 'ch' units, the layout automatically adjusts to maintain the same number of characters per line regardless of the user's font size or typeface choice. This approach potentially improves responsiveness and accessibility across diverse devices by ensuring the text remains legible and centered on the user's experience.

The Path Forward

While the 'ch' unit is already a part of the CSS standard, its adoption as a primary layout tool remains limited. The industry must now determine if a wholesale move away from pixels is practical for complex, multi-element grids or if 'ch' will remain a specialized tool for text-heavy containers. For now, Eden's proposal serves as a challenge to the status quo of absolute measurements in a world of fluid, user-defined typography, urging developers to prioritize the reading experience over rigid screen coordinates.