/favicon

name: favicon
description: Generate a complete set of favicons from a source image and update HTML. Use when setting up favicons for a web project.
argument-hint: [path to source image]

Generate a complete set of favicons from the source image at `$1` and update the project's HTML with the appropriate link tags.

Prerequisites

First, verify ImageMagick v7+ is installed by running:

which magick

If not found, stop and instruct the user to install it:

• **macOS**: `brew install imagemagick`
• **Linux**: `sudo apt install imagemagick`

Step 1: Validate Source Image

1. Verify the source image exists at the provided path: `$1` 2. Check the file extension is a supported format (PNG, JPG, JPEG, SVG, WEBP, GIF) 3. If the file doesn't exist or isn't a valid image format, report the error and stop

Note whether the source is an SVG file - if so, it will also be copied as `favicon.svg`.

Step 2: Detect Project Type and Static Assets Directory

Detect the project type and determine where static assets should be placed. Check in this order:

| Framework | Detection | Static Assets Directory | |-----------|-----------|------------------------| | **Rails** | `config/routes.rb` exists | `public/` | | **Next.js** | `next.config.*` exists | `public/` | | **Gatsby** | `gatsby-config.*` exists | `static/` | | **SvelteKit** | `svelte.config.*` exists | `static/` | | **Astro** | `astro.config.*` exists | `public/` | | **Hugo** | `hugo.toml` or `config.toml` with Hugo markers | `static/` | | **Jekyll** | `_config.yml` with Jekyll markers | Root directory (same as `index.html`) | | **Vite** | `vite.config.*` exists | `public/` | | **Create React App** | `package.json` has `react-scripts` dependency | `public/` | | **Vue CLI** | `vue.config.*` exists | `public/` | | **Angular** | `angular.json` exists | `src/assets/` | | **Eleventy** | `.eleventy.js` or `eleventy.config.*` exists | Check `_site` output or root | | **Static HTML** | `index.html` in root | Same directory as `index.html` |

**Important**: If existing favicon files are found (e.g., `favicon.ico`, `apple-touch-icon.png`), use their location as the target directory regardless of framework detection.

Report the detected project type and the static assets directory that will be used.

**When in doubt, ask**: If you are not 100% confident about where static assets should be placed (e.g., ambiguous project structure, multiple potential locations, unfamiliar framework), use `AskUserQuestionTool` to confirm the target directory before proceeding. It's better to ask than to put files in the wrong place.

Step 3: Determine App Name

Find the app name from these sources (in priority order):

1. **Existing `site.webmanifest`** - Check the detected static assets directory for an existing manifest and extract the `name` field 2. **`package.json`** - Extract the `name` field if it exists 3. **Rails `config/application.rb`** - Extract the module name (e.g., `module MyApp` → "MyApp") 4. **Directory name** - Use the current working directory name as fallback

Convert the name to title case if needed (e.g., "my-app" → "My App").

Step 4: Ensure Static Assets Directory Exists

Check if the detected static assets directory exists. If not, create it.

Step 5: Generate Favicon Files

Run these ImageMagick commands to generate all favicon files. Replace `[STATIC_DIR]` with the detected static assets directory from Step 2.

favicon.ico (multi-resolution: 16x16, 32x32, 48x48)

magick "$1" \
  \( -clone 0 -resize 16x16 \) \
  \( -clone 0 -resize 32x32 \) \
  \( -clone 0 -resize 48x48 \) \
  -delete 0 -alpha on -background none \
  [STATIC_DIR]/favicon.ico

favicon-96x96.png

magick "$1" -resize 96x96 -background none -alpha on [STATIC_DIR]/favicon-96x96.png

apple-touch-icon.png (180x180)

magick "$1" -resize 180x180 -background none -alpha on [STATIC_DIR]/apple-touch-icon.png

web-app-manifest-192x192.png

magick "$1" -resize 192x192 -background none -alpha on [STATIC_DIR]/web-app-manifest-192x192.png

web-app-manifest-512x512.png

magick "$1" -resize 512x512 -background none -alpha on [STATIC_DIR]/web-app-manifest-512x512.png

favicon.svg (only if source is SVG)

If the source file has a `.svg` extension, copy it:

cp "$1" [STATIC_DIR]/favicon.svg

Step 6: Create/Update site.webmanifest

Create or update `[STATIC_DIR]/site.webmanifest` with this content (substitute the detected app name):

{
  "name": "[APP_NAME]",
  "short_name": "[APP_NAME]",
  "icons": [
    {
      "src": "/web-app-manifest-192x192.png",
      "sizes": "192x192",
      "type": "image/png",
      "purpose": "maskable"
    },
    {
      "src": "/web-app-manifest-512x512.png",
      "sizes": "512x512",
      "type": "image/png",
      "purpose": "maskable"
    }
  ],
  "theme_color": "#ffffff",
  "background_color": "#ffffff",
  "display": "standalone"
}

If `site.webmanifest` already exists in the static directory, preserve the existing `theme_color`, `background_color`, and `display` values while updating the `name`, `short_name`, and `icons` array.

Step 7: Update HTML/Layout Files

Based on the detected project type, update the appropriate file. Adjust the `href` paths based on where the static assets directory is relative to the web root:

• If static files are in `public/` or `static/` and served from root → use `/favicon.ico`
• If static files are in `src/assets/` → use `/assets/favicon.ico`
• If static files are in the same directory as HTML → use `./favicon.ico` or just `favicon.ico`

For Rails Projects

Edit `app/views/layouts/application.html.erb`. Find the `<head>` section and add/replace favicon-related tags with:

<link rel="icon" type="image/png" href="/favicon-96x96.png" sizes="96x96" />
<link rel="icon" type="image/svg+xml" href="/favicon.svg" />
<link rel="shortcut icon" href="/favicon.ico" />
<link rel="apple-touch-icon" sizes="1