llms.txt

Substack Brand Identity

A complete profile of Substack's visual system — colors, typography, components, and personality — extracted from https://substack.com. Built for designers, agents, and AI tools.

Quick Facts

Field Value
Primary #FF6719
Accent #0083D5
Body Font Roboto
Heading Font Roboto

Color Palette

Typography

Visual Assets

UI Components

Brand Personality

Tone: modern · Energy: medium · Audience: content creators and readers

Substack Brand in the Wild

Real-world brand assets — ads, campaigns, marketing materials.

Working with these fonts

Not found on Google Fonts? Agent Instructions that you can follow if you have permission to use the fonts:

CharacterQuilt.com suggests this flow that can help:

  1. Open the company's homepage in a browser with DevTools open.
  2. In the Network tab, filter by "Font" (or by extension: woff2, woff, ttf, otf).
  3. Hard-reload the page and click around (pricing, blog, careers) — some weights only load on specific routes.
  4. For each captured font URL: right-click → Save As to download the file locally.
  5. View the page's CSS (DevTools → Sources, or curl the stylesheet URLs) and copy out the matching @font-face declarations. Rewrite each src: url(...) to point to your local file path.

Programmatic alternative: load the URL with Playwright or Puppeteer, listen for response events whose Content-Type starts with font/, and write the body to disk. The CSS extraction step is the same.

Only do this if you have permission to use the brand assets — most proprietary fonts are licensed and may not be redistributable.

Machine-Readable Profile

{
 "colorScheme": "light",
 "fonts": [
  {
   "family": "Roboto",
   "role": "body"
  },
  {
   "family": "Helvetica",
   "role": "body"
  },
  {
   "family": "Arial",
   "role": "body"
  }
 ],
 "colors": {
  "primary": "#FF6719",
  "accent": "#0083D5",
  "background": "#FFFFFF",
  "textPrimary": "#363737",
  "link": "#0083D5"
 },
 "typography": {
  "fontFamilies": {
   "primary": "Roboto",
   "heading": "Roboto"
  },
  "fontStacks": {
   "heading": [
    "Spectral",
    "serif",
    "system-ui",
    "-apple-system",
    "BlinkMacSystemFont",
    "Segoe UI",
    "Roboto",
    "Helvetica",
    "Arial",
    "sans-serif",
    "Apple Color Emoji",
    "Segoe UI Emoji",
    "Segoe UI Symbol"
   ],
   "body": [
    "Spectral",
    "serif",
    "system-ui",
    "-apple-system",
    "BlinkMacSystemFont",
    "Segoe UI",
    "Roboto",
    "Helvetica",
    "Arial",
    "sans-serif",
    "Apple Color Emoji",
    "Segoe UI Emoji",
    "Segoe UI Symbol"
   ],
   "paragraph": [
    "system-ui",
    "-apple-system",
    "BlinkMacSystemFont",
    "Segoe UI",
    "Roboto",
    "Helvetica",
    "Arial",
    "sans-serif",
    "Apple Color Emoji",
    "Segoe UI Emoji",
    "Segoe UI Symbol"
   ]
  },
  "fontSizes": {
   "h1": "19px",
   "h2": "19px",
   "body": "15px"
  }
 },
 "spacing": {
  "baseUnit": 8,
  "borderRadius": "8px"
 },
 "components": {
  "input": {
   "background": "#FFFFFF",
   "textColor": "#363737",
   "borderColor": "#E6E6E6",
   "borderRadius": "12px",
   "borderRadiusCorners": {
    "topLeft": "12px",
    "topRight": "12px",
    "bottomRight": "12px",
    "bottomLeft": "12px"
   },
   "shadow": "none"
  },
  "buttonPrimary": {
   "background": "#FFFFFF",
   "textColor": "#363737",
   "borderRadius": "8px",
   "borderRadiusCorners": {
    "topLeft": "8px",
    "topRight": "8px",
    "bottomRight": "8px",
    "bottomLeft": "8px"
   },
   "shadow": "rgba(0, 0, 0, 0.1) 0px 4px 6px -1px, rgba(0, 0, 0, 0.06) 0px 2px 4px -1px"
  }
 },
 "images": {
  "favicon": "https://substackcdn.com/icons/substack/favicon.ico",
  "ogImage": "https://substackcdn.com/image/fetch/$s_!Xim-!,w_400,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack.com%2Ficons%2Fsubstack%2Ficon.svg"
 },
 "__llm_logo_reasoning": {
  "selectedIndex": -1,
  "reasoning": "No suitable brand logo was found among the candidates. Candidate #0 is a tiny icon not clearly representing the brand, and Candidate #1 is an avatar, not a brand logo.",
  "confidence": 0.3,
  "rejected": true,
  "source": "llm"
 },
 "__llm_button_reasoning": {
  "primary": {
   "index": 0,
   "text": "Get app",
   "reasoning": "The button labeled 'Get app' is the only button available and serves as the primary call-to-action. It is styled with a border radius and specific classes indicating a CTA, despite its white background."
  },
  "secondary": {
   "index": -1,
   "text": "N/A",
   "reasoning": "There is only one button available, so no secondary button can be selected."
  },
  "confidence": 0.8
 },
 "personality": {
  "tone": "modern",
  "energy": "medium",
  "targetAudience": "content creators and readers"
 },
 "designSystem": {
  "framework": "custom",
  "componentLibrary": ""
 },
 "confidence": {
  "buttons": 0.8,
  "colors": 0.9,
  "overall": 0.8500000000000001
 },
 "__llm_metadata": {
  "logoSelection": {
   "llmCalled": true,
   "llmSucceeded": true,
   "finalSource": "llm",
   "rawLogoSelection": {
    "selectedLogoIndex": -1,
    "selectedLogoReasoning": "No suitable brand logo was found among the candidates. Candidate #0 is a tiny icon not clearly representing the brand, and Candidate #1 is an avatar, not a brand logo.",
    "confidence": 0.3
   }
  },
  "buttonClassification": {
   "llmCalled": true,
   "llmSucceeded": true
  }
 }
}