Weight
React + Tailwind
import { useState } from 'react';
const NAMES = ['Thin', 'Extra light', 'Light', 'Regular', 'Medium', 'Semibold', 'Bold', 'Extra bold', 'Black'];
const css = `
.slider-weight { display: grid; justify-items: center; gap: 10px; width: 220px; }
.slider-weight__sample { color: light-dark(#373a40, #f1f2f3); font-family: system-ui, -apple-system, 'Segoe UI', sans-serif; font-size: 68px; line-height: 1; letter-spacing: -0.02em; font-weight: calc(100 + var(--slider-weight-v) * 800); transition: font-weight 0.2s; }
.slider-weight__name { color: light-dark(#50535b, #c6c8cd); font-size: 12px; }
.slider-weight__name b { color: light-dark(#373a40, #f1f2f3); font-weight: 600; font-variant-numeric: tabular-nums; }
.slider-weight__track { position: relative; width: 100%; height: 24px; }
.slider-weight__rail { position: absolute; left: 0; right: 0; top: 7px; height: 10px; background: light-dark(#dbdde1, #2e3035); clip-path: polygon(0 45%, 100% 0, 100% 100%, 0 55%); }
.slider-weight__thumb { position: absolute; top: 2px; left: calc(var(--slider-weight-v) * (100% - 20px)); width: 20px; height: 20px; border-radius: 50%; background: light-dark(#373a40, #f1f2f3); box-shadow: 0 0 0 3px light-dark(#f3f4f7, #1a1c1f), 0 2px 6px light-dark(rgba(0, 0, 0, 0.12), rgba(0, 0, 0, 0.4)); }
.slider-weight:has(.slider-weight__input:focus-visible) .slider-weight__thumb { outline: 2px solid light-dark(#50535b, #c6c8cd); outline-offset: 4px; }
.slider-weight__input { position: absolute; inset: 0; width: 100%; height: 100%; margin: 0; opacity: 0; cursor: pointer; -webkit-appearance: none; appearance: none; background: none; }
.slider-weight__input::-webkit-slider-thumb { -webkit-appearance: none; width: 20px; height: 20px; }
.slider-weight__input::-moz-range-thumb { width: 20px; height: 20px; border: 0; }
@media (prefers-reduced-motion: reduce) {
.slider-weight__sample { transition: none; }
}
`;
export function WeightSlider() {
const [w, setW] = useState(400);
const v = (w - 100) / 800;
return (
<>
<style>
{css}
</style>
<div className="slider-weight" style={{ '--slider-weight-v': v } as React.CSSProperties}>
<span className="slider-weight__sample" aria-hidden="true">
Aa
</span>
<span className="slider-weight__name" aria-hidden="true">
{NAMES[Math.round(v * 8)]} <b>{w}</b>
</span>
<div className="slider-weight__track">
<span className="slider-weight__rail" />
<span className="slider-weight__thumb" />
<input
className="slider-weight__input"
type="range"
min={100}
max={900}
step={10}
value={w}
onChange={(e) => setW(+e.target.value)}
aria-label="Font weight"
aria-valuetext={`${w}, ${NAMES[Math.round(v * 8)]}`}
/>
</div>
</div>
</>
);
}Markup where the component goes, CSS in your stylesheet, script before </body>. In Vue, Svelte or Angular, call initSliderWeight(el) on the mounted element instead.
HTML
<div class="slider-weight" style="--slider-weight-v:0.375">
<span class="slider-weight__sample" aria-hidden="true">Aa</span>
<span class="slider-weight__name" aria-hidden="true">Regular <b>400</b></span>
<div class="slider-weight__track">
<span class="slider-weight__rail"></span>
<span class="slider-weight__thumb"></span>
<input class="slider-weight__input" type="range" min="100" max="900" step="10" aria-label="Font weight" aria-valuetext="400, Regular" value="400"/>
</div>
</div>CSS
.slider-weight { display: grid; justify-items: center; gap: 10px; width: 220px; }
.slider-weight__sample { color: light-dark(#373a40, #f1f2f3); font-family: system-ui, -apple-system, 'Segoe UI', sans-serif; font-size: 68px; line-height: 1; letter-spacing: -0.02em; font-weight: calc(100 + var(--slider-weight-v) * 800); transition: font-weight 0.2s; }
.slider-weight__name { color: light-dark(#50535b, #c6c8cd); font-size: 12px; }
.slider-weight__name b { color: light-dark(#373a40, #f1f2f3); font-weight: 600; font-variant-numeric: tabular-nums; }
.slider-weight__track { position: relative; width: 100%; height: 24px; }
.slider-weight__rail { position: absolute; left: 0; right: 0; top: 7px; height: 10px; background: light-dark(#dbdde1, #2e3035); clip-path: polygon(0 45%, 100% 0, 100% 100%, 0 55%); }
.slider-weight__thumb { position: absolute; top: 2px; left: calc(var(--slider-weight-v) * (100% - 20px)); width: 20px; height: 20px; border-radius: 50%; background: light-dark(#373a40, #f1f2f3); box-shadow: 0 0 0 3px light-dark(#f3f4f7, #1a1c1f), 0 2px 6px light-dark(rgba(0, 0, 0, 0.12), rgba(0, 0, 0, 0.4)); }
.slider-weight:has(.slider-weight__input:focus-visible) .slider-weight__thumb { outline: 2px solid light-dark(#50535b, #c6c8cd); outline-offset: 4px; }
.slider-weight__input { position: absolute; inset: 0; width: 100%; height: 100%; margin: 0; opacity: 0; cursor: pointer; -webkit-appearance: none; appearance: none; background: none; }
.slider-weight__input::-webkit-slider-thumb { -webkit-appearance: none; width: 20px; height: 20px; }
.slider-weight__input::-moz-range-thumb { width: 20px; height: 20px; border: 0; }
@media (prefers-reduced-motion: reduce) {
.slider-weight__sample { transition: none; }
}JavaScript
function initSliderWeight(root) {
var NAMES = ['Thin', 'Extra light', 'Light', 'Regular', 'Medium', 'Semibold', 'Bold', 'Extra bold', 'Black'];
var input = root.querySelector('.slider-weight__input');
var name = root.querySelector('.slider-weight__name');
var num = name.querySelector('b');
function update() {
var w = +input.value;
var v = (w - 100) / 800;
var label = NAMES[Math.round(v * 8)];
root.style.setProperty('--slider-weight-v', v);
num.textContent = w;
name.replaceChildren(label + ' ', num);
input.setAttribute('aria-valuetext', w + ', ' + label);
}
input.addEventListener('input', update);
update();
return function () { input.removeEventListener('input', update); };
}
document.querySelectorAll('.slider-weight').forEach(initSliderWeight);Goal: Create a "Weight" slider.
Visual behavior: A font-weight slider: the sample letters thicken from Thin to Black as you drag, and the weight name and number change below.
Technique:
- A real <input type="range"> lies over the drawing, transparent (opacity 0, appearance none), with its thumb hit area sized to the drawn thumb, so dragging, clicking the track and the arrow, Page Up/Down, Home and End keys all work natively. The drawing is aria-hidden.
- The value is written to one CSS custom property (0 to 1) on the root; the sample sets font-weight to calc(100 + value * 800) in the system font, which is variable on current systems, so the weight changes smoothly.
- The range steps by 10 and the aria-valuetext gives the number and its name.
- :has(input:focus-visible) outlines the drawn thumb, so keyboard focus is visible though the input itself is not.
Accessibility: A native range input with an aria-label and an aria-valuetext in words, so a screen reader announces the reading rather than a bare number; keyboard focus outlines the drawn thumb. Under prefers-reduced-motion the sample changes weight without a transition.
My stack: {{USER_STACK}}
My styling: {{USER_STYLING}}
My constraints: {{USER_CONSTRAINTS}}
My colors: neutral only. Black, white and grays, no hues. Use the color values above as written, or my project's closest neutral tokens.
Return a single self-contained component. No dependencies.Goal: Create a "Weight" slider.
Visual behavior: A font-weight slider: the sample letters thicken from Thin to Black as you drag, and the weight name and number change below.
Technique:
- A real <input type="range"> lies over the drawing, transparent (opacity 0, appearance none), with its thumb hit area sized to the drawn thumb, so dragging, clicking the track and the arrow, Page Up/Down, Home and End keys all work natively. The drawing is aria-hidden.
- The value is written to one CSS custom property (0 to 1) on the root; the sample sets font-weight to calc(100 + value * 800) in the system font, which is variable on current systems, so the weight changes smoothly.
- The range steps by 10 and the aria-valuetext gives the number and its name.
- :has(input:focus-visible) outlines the drawn thumb, so keyboard focus is visible though the input itself is not.
Accessibility: A native range input with an aria-label and an aria-valuetext in words, so a screen reader announces the reading rather than a bare number; keyboard focus outlines the drawn thumb. Under prefers-reduced-motion the sample changes weight without a transition.
My stack: {{USER_STACK}}
My styling: {{USER_STYLING}}
My constraints: {{USER_CONSTRAINTS}}
My colors: use my project's existing color tokens. The color values above are grayscale placeholders. Map each one by its role (surface, text, border, accent, glow) to my theme, and keep their relative lightness so contrast and the effect still read.
Return a single self-contained component. No dependencies.Paste into Claude, ChatGPT or Cursor after filling in {{USER_STACK}}, {{USER_STYLING}} and {{USER_CONSTRAINTS}}. Neutral keeps the greys you see here; Match my project asks the model to map them onto your own colour tokens.
Free to use in any project, commercial included. MIT-0, no attribution required. Licence
About this component
A font-weight slider: the sample letters thicken from Thin to Black as you drag, and the weight name and number change below.
- Dependencies
- None
- Difficulty
- Beginner
- Triggers
- state change, morph
- Techniques
- css variables, css transition
- Reduced motion
- Respected
- Theme
- Light and dark (follows your page's color-scheme)
A native range input with an aria-label and an aria-valuetext in words, so a screen reader announces the reading rather than a bare number; keyboard focus outlines the drawn thumb. Under prefers-reduced-motion the sample changes weight without a transition.