Reference category

Design & frontend

A design value only survives handoff when its unit and colour space are explicit. Pixels are absolute, rem follows the root font size, em follows the parent, and viewport units follow the viewport — the same number can therefore mean different things in two places. Colour formats have the same problem: sRGB hex, HSL and CMYK describe different things and do not convert losslessly.

These entries explain what each unit or colour format actually measures, where it breaks, and how to choose between them. The paired converters show the arithmetic so you can confirm a value instead of trusting a screenshot.

Reference sets in this category (2)

Color Format Reference

Hex, RGB, HSL, HSV, CMYK, alpha and WCAG contrast explained with exact ranges and formulas — each entry paired with a converter that runs in your browser.

10 entries →

CSS Unit Reference

How CSS length units actually resolve: px, rem, em, ch, ex, viewport units, percentages, grid fr and calc/clamp. Facts from the CSS Values specification, paired with a px/rem converter.

10 entries →

All 20 entries

Color Format Reference 10 entries

Hex color#RRGGBB notation, its shorthand forms and the 8-digit alpha variant. RGB colorThree sRGB channels from 0 to 255, plus optional alpha. HSL colorHue in degrees, saturation and lightness in percent. HSV / HSB colorHue, saturation and value — the model behind most color pickers. CMYK colorSubtractive cyan, magenta, yellow and key (black) for print. CSS named colorsAbout 148 keyword colors, from aliceblue to yellowgreen. Alpha channelOpacity from fully transparent to fully opaque, in 0–1 or 0–255. WCAG contrast ratioThe 4.5:1 and 3:1 thresholds for readable text and UI components. Relative luminanceThe WCAG brightness measure behind contrast ratios. sRGB gamutThe default web color space, and what happens outside it.

CSS Unit Reference 10 entries

pxThe CSS pixel is a reference unit: 96 CSS pixels equal one inch. remOne rem equals the root element's font size, typically 16px. emOne em equals the current element's computed font size and compounds through nesting. ch and exch is the width of the digit zero; ex is the font's x-height. vw and vhOne vw is 1% of the viewport width; one vh is 1% of the viewport height. dvh, svh and lvhDynamic, small and large viewport units describe the height as browser chrome shows or hides. vmin and vmaxvmin is 1% of the smaller viewport side; vmax is 1% of the larger side. %A percentage resolves against a property-specific reference, often the parent's size. frThe fr unit distributes free space in a CSS grid track. calc, min, max and clampThese functions combine lengths and bound them without JavaScript.

Reference sets in this category (2)

Color Format Reference

CSS Unit Reference

All 20 entries

Color Format Reference 10 entries

CSS Unit Reference 10 entries

Tools that work with these entries

Color Converter

Unit Converter

PX to REM Converter

Word Counter

Percentage Calculator

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