# Semantic UI design system

> Semantic UI design system measured from semantic-ui.com: Lato font, #1B1C1D primary on #FFFFFF, 17 color hex codes, type scale, spacing and a free DESIGN.md.

Canonical page: https://sitepeel.dev/design-md/semantic-ui.com/

Semantic UI’s website (semantic-ui.com) uses the Lato font and #1B1C1D as its main color on a white background. Measured by Sitepeel on November 4, 2026.

## What font does Semantic UI use?

Semantic UI uses Lato (weights 400 and 700) on semantic-ui.com. Page titles are 40px at weight 400 (32px on phones) and body text is 14px. Measured on November 4, 2026.

- Lato (weights 400, 700)

## Semantic UI colors: palette and hex codes

Semantic UI’s main colors are #FFFFFF (white) for the background, #212121 (charcoal) for text and #1B1C1D (charcoal) as the main accent, with #4183C4 (blue) and #008C79 (dark teal) as other accents. Measured on November 4, 2026.

- #FFFFFF: white
- #212121: charcoal
- #666666: slate
- #858188: cool gray
- #8D8A8A: gray
- #F3F4F5: snow
- #E8E8E8: mist
- #E0E1E2: mist

## What is Semantic UI built with?

Semantic UI’s website (semantic-ui.com) is built with jQuery, Cloudflare, GitHub Pages and Google Fonts. Measured on November 4, 2026.

- JavaScript framework: jQuery 3.1.1
- Hosting & CDN: Cloudflare, GitHub Pages
- Analytics: Cloudflare Web Analytics, Google Analytics
- Fonts & icons: Google Fonts

## Questions and answers

### What font does Semantic UI use?

Semantic UI’s website uses Lato (weights 400 and 700). Page titles are 40px at weight 400 (32px on phones) and body text is 14px. Measured on November 4, 2026.

### What are the Semantic UI colors and hex codes?

On semantic-ui.com: #FFFFFF (white) for the background, #212121 (charcoal) for text and #1B1C1D (charcoal) as the main accent, with #4183C4 (blue) and #008C79 (dark teal) as other accents. The color palette above lists all 17 colors with their hex codes and where each one is used.

### What is the Semantic UI design system?

The design system on this page is semantic-ui.com’s, as measured on November 4, 2026: Lato type, #1B1C1D as the main color and 4px corners, written down as a DESIGN.md. It is not Semantic UI’s own documentation.

### What is Semantic UI built with?

Semantic UI’s website (semantic-ui.com) is built with jQuery, Cloudflare, GitHub Pages and Google Fonts. The full tech stack Sitepeel found: jQuery, Cloudflare, Cloudflare Web Analytics, Google Fonts, Google Analytics and GitHub Pages. Measured on November 4, 2026.

### What is the Semantic UI DESIGN.md?

A plain-text file with Semantic UI’s measured colors, type, spacing, corners and components as tokens, plus short rules, in the DESIGN.md format Google published with Stitch. Your AI coding agent reads it and builds in this style. More about DESIGN.md.

### How do I use it with Claude Code or Cursor?

Download the file and put it in your project’s root folder, then ask your agent to follow DESIGN.md. Step-by-step guides: Claude Code, Cursor, Codex, GitHub Copilot.

### Is this Semantic UI’s official design system?

No. Sitepeel measured it from semantic-ui.com’s public page on November 4, 2026. It is an independent analysis, not made or approved by Semantic UI.

### Can I use Semantic UI’s style in my own product?

Use it to learn, prototype and compare. For a real product, make the style your own, and never copy Semantic UI’s logo, name, pictures or text.

### How accurate are the values?

Each value was measured on the rendered page after it fully loaded, on desktop and mobile: colors where they appear, type with tracking, spacing, corners, shadows and hover states. Sites change, so check the date at the top.

## Files

- [DESIGN.md](https://sitepeel.dev/design-md/semantic-ui.com/DESIGN.md): the plain file to put in your project.
- [All brand DESIGN.md files](https://sitepeel.dev/design-md/examples/index.md)

Independent analysis by Sitepeel (sitepeel.dev), not affiliated with Semantic UI.

## The DESIGN.md file

```markdown
---
version: alpha
name: Semantic UI
description: "Light monochrome interface measured from semantic-ui.com: Lato type, tonal surfaces and 4px corners."
colors:
  background: "#FFFFFF"
  surface: "#FFFFFF"
  on-surface: "#212121"
  on-background: "#212121"
  on-surface-variant: "#666666"
  on-surface-muted: "#858188"
  on-surface-subtle: "#8D8A8A"
  surface-container-low: "#F3F4F5"
  surface-container: "#E8E8E8"
  surface-container-high: "#E0E1E2"
  overlay: "#0000000D"
  overlay-strong: "#2224261A"
  outline: "#22242626"
  outline-variant: "#D4D4D5"
  primary: "#1B1C1D"
  on-primary: "#FFFFFF"
  secondary: "#4183C4"
  tertiary: "#008C79"
  warning: "#573A08"
typography:
  headline-display:
    fontFamily: Lato
    fontSize: 40px
    fontWeight: 400
    lineHeight: 1.29
  headline-lg:
    fontFamily: Lato
    fontSize: 26px
    fontWeight: 400
    lineHeight: 1.29
  headline-md:
    fontFamily: Lato
    fontSize: 20px
    fontWeight: 400
    lineHeight: 1.29
  body-md:
    fontFamily: Lato
    fontSize: 14px
    fontWeight: 400
    lineHeight: 1.43
  body-lg:
    fontFamily: Lato
    fontSize: 18px
    fontWeight: 700
    lineHeight: 1.29
  label-lg:
    fontFamily: Lato
    fontSize: 16px
    fontWeight: 700
    lineHeight: 1
  label-md:
    fontFamily: Lato
    fontSize: 15px
    fontWeight: 700
    lineHeight: 1.29
  label-sm:
    fontFamily: Lato
    fontSize: 14px
    fontWeight: 700
    lineHeight: 1
  headline-display-mobile:
    fontFamily: Lato
    fontSize: 32px
    fontWeight: 400
    lineHeight: 1.29
rounded:
  sm: 2px
  md: 4px
spacing:
  xs: 3px
  sm: 7px
  md: 14px
  lg: 18px
components:
  button-primary:
    backgroundColor: "{colors.primary}"
    textColor: "{colors.on-primary}"
    rounded: "{rounded.md}"
    padding: 7px 10px
    height: 26px
  button-primary-hover:
    backgroundColor: "#27292A"
  button-ghost:
    textColor: "{colors.on-primary}"
    typography: "{typography.headline-md}"
    rounded: "{rounded.md}"
    padding: 15.71px 30px
  input-field:
    backgroundColor: "{colors.background}"
    textColor: "#000000"
    typography: "{typography.body-md}"
    rounded: "{rounded.sm}"
    padding: 7px
  card:
    backgroundColor: "{colors.background}"
    textColor: "{colors.on-surface}"
    typography: "{typography.body-md}"
    rounded: "{rounded.md}"
    padding: 0px
  link:
    textColor: "{colors.secondary}"
---

# Semantic UI Design System

## Overview

Semantic UI describes itself as: “Semantic empowers designers and developers by creating a shared vocabulary for UI.” The interface is light, built on **White (#FFFFFF)** with **Charcoal (#212121)** text and almost no color: actions are carried by contrast, not hue.

Type is set in **Lato**. Headlines run large; body text is 14px. Depth comes from hairline borders and inset highlights rather than drop shadows. Corners are mostly 4px.

Measured from [semantic-ui.com](https://semantic-ui.com/) on November 4, 2026 at 1440×900 and 390×844 from 219 rendered elements. Values are computed styles from the live page, not the original source files.

## Colors

The palette has 17 roles.

- **White (#FFFFFF):** Page background, seen 12 times. Token `background`.
- **Charcoal (#212121):** Primary text and headings. Token `on-surface`.
- **Slate (#666666):** Secondary text, seen 8 times. Token `on-surface-variant`.
- **Cool Gray (#858188):** Muted text and metadata, seen 52 times. Token `on-surface-muted`.
- **Gray (#8D8A8A):** Subtle text and placeholders, seen 15 times. Token `on-surface-subtle`.
- **Snow (#F3F4F5):** Raised areas one step from the page, seen 2 times. Token `surface-container-low`.
- **Mist (#E8E8E8):** Cards and panels, seen 4 times. Token `surface-container`.
- **Mist (#E0E1E2):** Hover and pressed fills, seen 4 times. Token `surface-container-high`.
- **Near Black 5% (#0000000D):** Translucent fill for cards and controls, seen 2 times. Token `overlay`.
- **Graphite 10% (#2224261A):** Stronger translucent fill, seen 1 time. Token `overlay-strong`.
- **Graphite 15% (#22242626):** Borders and dividers, seen 9 times. Token `outline`.
- **Silver (#D4D4D5):** Secondary dividers, seen 1 time. Token `outline-variant`.
- **Charcoal (#1B1C1D):** Primary buttons and calls to action, seen 9 times. Token `primary`.
- **White (#FFFFFF):** Text and icons on primary. Token `on-primary`.
- **Blue (#4183C4):** Accent in text, fills and borders, seen 22 times. Token `secondary`.
- **Dark Teal (#008C79):** Accent in text, fills and borders, seen 21 times. Token `tertiary`.
- **Deep Orange (#573A08):** Warnings and highlights, seen 4 times. Token `warning`.

## Typography

**Lato** carries the whole interface. Fallback stack: `Lato, Helvetica Neue, Arial, Helvetica`. Other loaded fonts: Icons, Accordion, Checkbox, Dropdown.

- **headline-display:** Lato 40px at weight 400, line height 1.29 (32px on mobile). Page title (h1).
- **headline-lg:** Lato 26px at weight 400, line height 1.29. Section headings (h2).
- **headline-md:** Lato 20px at weight 400, line height 1.29. Sub-section headings.
- **body-md:** Lato 14px at weight 400, line height 1.43. Body text.
- **body-lg:** Lato 18px at weight 700, line height 1.29. Lead paragraphs.
- **label-lg:** Lato 16px at weight 700, line height 1. Large buttons and tabs.
- **label-md:** Lato 15px at weight 700, line height 1.29. Buttons, navigation and labels.
- **label-sm:** Lato 14px at weight 700, line height 1. Small labels and badges.

## Layout

Spacing does not follow a strict grid: 34% of measured values are multiples of 4px, so match the measured steps rather than rounding to a grid.

- **Scale:** xs 3px, sm 7px, md 14px, lg 18px.
- **Breakpoints:** 320px, 400px, 500px, 767px, 768px, 820px, 991px, 992px, 1144px, 1145px, 1199px, 1200px, 1272px, 1500px, 1919px, 1920px.

## Elevation & Depth

Depth comes mostly from hairline rings and inset highlights on tonal surfaces (#F3F4F5 → #E8E8E8 → #E0E1E2):

- `rgba(34, 36, 38, 0.15) 0px 0px 0px 0px inset`
- `rgba(0, 0, 0, 0) 0px 0px 0px 1px inset, rgba(34, 36, 38, 0.15) 0px 0px 0px 0px inset`
- `rgb(255, 255, 255) 0px 0px 0px 2px inset`

A few raised panels add a soft drop shadow: `rgba(34, 36, 38, 0.15) 0px 1px 2px 0px`.

## Shapes

Most elements use 4px corners. Measured radii, most used first:

- **md (4px):** 102 elements.
- **sm (2px):** 4 elements.

## Components

Measured from the rendered page. Token values reference the tokens above.

- **button-primary (“2.5.0”):** #1B1C1D fill, #FFFFFF text, 12px/700, 4px radius, padding 7px 10px.
- **button-primary-hover:** background #27292A, text #FFFFFF on hover.
- **button-ghost (“Get Started”):** transparent fill, #FFFFFF text, 20px/700, 4px radius, padding 15.71px 30px, shadow `rgb(255, 255, 255) 0px 0px 0px 2px inset`.
- **input-field:** #FFFFFF fill, #000000 text, 14px/400, 2px radius, padding 7px, border 1px solid #22242626.
- **card:** #FFFFFF fill, #000000DE text, 14px/400, 4px radius, padding 0px, shadow `rgb(212, 212, 213) 0px 1px 3px 0px, rgb(212, 212, 213) 0px 0px 0px 1px`.
- **link:** transparent fill, #4183C4 text, padding 0px.

## Do's and Don'ts

- Do use #FFFFFF for the page and lift surfaces in small steps: #F3F4F5, #E8E8E8, #E0E1E2.
- Do keep text in 4 levels: #212121, #666666, #858188, #8D8A8A.
- Do let contrast carry emphasis; primary actions use #1B1C1D on #FFFFFF.
- Do reuse the measured spacing steps (7px, 14px, 18px).
- Do use 4px corners on most elements; larger surfaces also use 2px.
- Don't use #858188 for body text; it reaches 3.82:1 on #FFFFFF. Keep it for large text or metadata.
- Don't use #8D8A8A for body text; it reaches 3.42:1 on #FFFFFF. Keep it for large text or metadata.
- Don't use heavy drop shadows; keep depth to hairline rings and tonal surfaces.
- Don't introduce new font families beyond Lato.
- Don't add saturated accent colors; the measured palette is almost entirely neutral.
- Don't make interface transitions slower than 0.5s.

## Motion

Interface transitions are quick: 0.1s, 0.5s.

- **Easing:** `ease`.

Generated by [Sitepeel](https://sitepeel.dev/design-md/semantic-ui.com/), the free DESIGN.md generator (engine 2026.10.29+b828a475ee10).

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