MozaikaDesign system

Substack — Design System

light · modern · medium · custom · confidence 92%

The full decoded design system for Substack: color roles, type scale, spacing, radii and paste-ready DESIGN.md / Tailwind / CSS exports.

Open in Mozaika →

This is a static, crawlable rendering for search & AI engines. The interactive version — filters, live decode console, copy & export — is at https://mozaika.design/ds/substack.

Tokens

Substack's decoded design system: background #FFFFFF, text #363737, accent #0083D5, link #0083D5, primary #FF6719; type scale h1 19px / h2 19px / body 15px; 8px spacing base; 8px base radius. The single interactive/action color is #FFFFFF — used only on interactive or must-notice elements (buttons, links, key highlights), never on large fills.

Color roles

RoleValue
bg#FFFFFF
surface#F2F3F3
border#E0E1E1
text#363737
text_muted#828383
primary#FF6719
accent#0083D5
link#0083D5
button_bg#FFFFFF
button_text#363737

Using these colors

Typography

Spacing

Radii

Shadow

rgba(0, 0, 0, 0.1) 0px 4px 6px -1px, rgba(0, 0, 0, 0.06) 0px 2px 4px -1px

Export: DESIGN.md

# Substack — Design System

> light, modern, medium, custom

## Colors

| Role | Value |
|------|-------|
| bg | `#FFFFFF` |
| surface | `#F2F3F3` |
| border | `#E0E1E1` |
| text | `#363737` |
| text_muted | `#828383` |
| primary | `#FF6719` |
| accent | `#0083D5` |
| link | `#0083D5` |
| button_bg | `#FFFFFF` |
| button_text | `#363737` |

**Using these colors**

- **Action color** `#FFFFFF` — the single interactive color; it appears only on things you click or must notice (buttons, key highlights), never on large fills or backgrounds.
- `accent`, `link` are all `#0083D5` — one role, not several.
- **accent** `#0083D5` — accent for emphasis — keep it rare on the page.
- **primary** `#FF6719` — a brand color — but the call-to-action uses #FFFFFF, not this.

## Typography

- Heading: **Segoe UI** _(free fallback: Newsreader)_
- Body: **Segoe UI** _(free fallback: Newsreader)_

| Role | Size / weight · line-height · tracking |
|------|------------------------------------------|
| hero | 32px / 500 · lh 40px |
| h2 | 24px / 500 · lh 30px |
| h3 | 20px / 700 · lh 24px |
| body | 15px / 500 · lh 20px |
| small | 13px / 400 · lh 20px |

- Weight ladder: 400 · 500 · 600 · 700 · 800 — use these exact measured weights, not the 400/600 defaults.

> **Fonts —** Segoe UI may be proprietary — safe free fallback: Newsreader (Google Fonts).

## Spacing
- base unit: 8px
- scale: 4px, 8px, 12px, 16px, 24px, 32px, 48px, 64px

## Radius
- base: 8px
- button: 8px
- card: 8px
- pill: 9999px

## Primary button
- bg `#FFFFFF` · text `#363737` · radius 8px

## How to apply
Paste the Tailwind `@theme` (or CSS variables) as your base, then build each
section to its spec — verify every color, radius, and font against these tokens.

---

> **Decoded with Mozaika** — measured live, not guessed. Full decoded design system + one-command install: mozaika.design/ds/substack

Export: Tailwind v4 (@theme)

@theme {
  /* action color #FFFFFF — the one interactive color; buttons/links/emphasis only, never large fills. */
  --color-bg: #FFFFFF;
  --color-surface: #F2F3F3;
  --color-border: #E0E1E1;
  --color-text: #363737;
  --color-text-muted: #828383;
  --color-primary: #FF6719;  /* a brand color — but the call-to-action uses #FFFFFF, not this. */
  --color-accent: #0083D5;  /* accent for emphasis — keep it rare on the page. */
  --color-link: #0083D5;  /* inline text links and link-styled controls. */
  --color-button-bg: #FFFFFF;  /* primary-button fill — the main call-to-action color. */
  --color-button-text: #363737;
  /* fonts: Segoe UI may be proprietary — safe free fallback: Newsreader (Google Fonts). */
  --font-heading: "Segoe UI", "Newsreader", system-ui, -apple-system, 'Segoe UI', sans-serif;
  --font-body: "Segoe UI", "Newsreader", system-ui, -apple-system, 'Segoe UI', sans-serif;
  /* measured weights: 400, 500, 600, 700, 800 — use these, not 400/600 */
  --text-hero: 32px; --font-weight-hero: 500; --leading-hero: 40px;
  --text-h2: 24px; --font-weight-h2: 500; --leading-h2: 30px;
  --text-h3: 20px; --font-weight-h3: 700; --leading-h3: 24px;
  --text-body: 15px; --font-weight-body: 500; --leading-body: 20px;
  --text-small: 13px; --font-weight-small: 400; --leading-small: 20px;
  --radius-base: 8px;
  --radius-button: 8px;
  --radius-card: 8px;
  --radius-pill: 9999px;
  --spacing-1: 4px;
  --spacing-2: 8px;
  --spacing-3: 12px;
  --spacing-4: 16px;
  --spacing-5: 24px;
  --spacing-6: 32px;
  --spacing-7: 48px;
  --spacing-8: 64px;
}

Export: CSS variables

:root {
  /* action color #FFFFFF — the one interactive color; buttons/links/emphasis only, never large fills. */
  --bg: #FFFFFF;
  --surface: #F2F3F3;
  --border: #E0E1E1;
  --text: #363737;
  --text-muted: #828383;
  --primary: #FF6719;  /* a brand color — but the call-to-action uses #FFFFFF, not this. */
  --accent: #0083D5;  /* accent for emphasis — keep it rare on the page. */
  --link: #0083D5;  /* inline text links and link-styled controls. */
  --button-bg: #FFFFFF;  /* primary-button fill — the main call-to-action color. */
  --button-text: #363737;
  --font-heading: "Segoe UI", "Newsreader", system-ui, -apple-system, 'Segoe UI', sans-serif;
  --font-body: "Segoe UI", "Newsreader", system-ui, -apple-system, 'Segoe UI', sans-serif;
  --text-hero: 32px; --weight-hero: 500; --leading-hero: 40px;
  --text-h2: 24px; --weight-h2: 500; --leading-h2: 30px;
  --text-h3: 20px; --weight-h3: 700; --leading-h3: 24px;
  --text-body: 15px; --weight-body: 500; --leading-body: 20px;
  --text-small: 13px; --weight-small: 400; --leading-small: 20px;
  --radius: 8px;
  --radius-button: 8px;
  --radius-card: 8px;
  --radius-pill: 9999px;
}
/* fonts: Segoe UI may be proprietary — safe free fallback: Newsreader (Google Fonts). */