bm-favicon-creator

name	bm-favicon-creator
description	Generate a complete favicon set (SVG, PNGs, multi-resolution .ico, Apple touch icon) from a Lucide icon (default) or another source SVG, then wire the favicon meta tags into the codebase. Use when the user wants to set up a favicon, replace a placeholder favicon, or brand the app icon.
user_invocable	true

Favicon Creator

Generate a complete, cross-device favicon set and wire it into the project's layout so it shows up correctly in every browser, tab, home screen, and pinned shortcut.

The favicon is always rendered as a square with tight rounded corners, with the chosen icon centered inside on a solid background color.

Prerequisites

Requires rsvg-convert and ImageMagick's magick on the system. If either is missing, stop and ask the user to install them (brew install librsvg imagemagick). Do not attempt a workaround.

Step 1 — Gather inputs from the user

Ask each question in order. Wait for an answer before moving on. Do not assume defaults beyond what is specified.

1.1 Icon source

Ask: "What icon do you want to use? You can:

• Name a Lucide icon (e.g. rocket, sparkles, book-open) — this is the default
• Name an icon from a different icon library (and which library)
• Point me to an existing .svg file in the repo
• Describe the icon you want and I'll generate the SVG"

Resolve the answer:

• Default — Lucide icon by name. If the user names an icon without naming a library, treat it as a Lucide icon. Fetch the exact SVG from lucide.dev for that icon and use it as the source. Lucide icons use stroke="currentColor" and fill="none". Always set stroke-width="1.5" on the root <svg> element (override whatever value Lucide ships with). Do not redraw, simplify, or recreate the paths — use the exact paths from Lucide.
• Other icon library. If the user names a different library (e.g. Heroicons, Phosphor, Tabler, Material Symbols), fetch the exact SVG from that library's official source.
• Existing SVG path. Read the file and confirm the viewBox / intrinsic size. If there is no viewBox, derive one from width/height.
• Described icon. Generate a minimal SVG matching the description. Keep it geometric and legible at 16×16.

1.2 Background color

Ask: "What background color should the favicon square use? (hex, e.g. #FCF8F2)"

This fills the rounded square and also becomes the page theme-color meta tag value.

1.3 Icon color

Ask: "What color should the icon itself be? (hex, e.g. #22D3EE)"

For Lucide / stroke-based icons, this becomes the stroke color. For filled icons, this becomes the fill color.

Confirm both colors back to the user before generating.

Step 2 — Locate the layout file

Find where favicon <link> tags should live. First, read CLAUDE.md and/or AGENTS.md if they exist — they may declare a convention for where head/meta tags go.

If no convention is declared, check in this order:

• Next.js (app router): app/layout.tsx / app/layout.jsx — favicons are typically handled via file conventions (app/icon.*, app/apple-icon.*) and/or a metadata export
• Next.js (pages router): pages/_document.tsx / pages/_app.tsx
• Rails: app/views/layouts/application.html.erb (or .haml, .slim)
• Vite/React (Inertia, SPA): index.html or app/views/layouts/application.html.erb
• SvelteKit: src/app.html
• Astro: src/layouts/*.astro or individual page layouts
• Plain HTML: index.html

If you can't find the layout, grep for rel="icon" or apple-touch-icon across the repo. If still ambiguous, ask the user.

Step 3 — Determine the public asset directory

Always look for a public/ folder first. Most modern frameworks use it, and the four canonical files (favicon.ico, icon.png, icon.svg, apple-touch-icon.png) must always land there if it exists.

If the project also has another conventional asset location (e.g. Next.js app router's app/ directory for file-convention icons), write there in addition — but public/ is always required.

If neither exists, ask the user where assets should go, then ensure a public/ equivalent.

Step 4 — Generate the SVG for browser tabs (rounded square with centered icon)

Write public/icon.svg as a square with tight rounded corners, the background color filling the square, and the source icon centered inside. After writing it, also copy the same file to public/favicon.svg (some browsers and link-preview crawlers look for favicon.svg at the site root by name).

Canvas: 80 × 80. Corner radius: 16 (tight rounded corners — 20% of the canvas).

The inner icon should occupy ~60% of the canvas (safe zone for iOS rounded corner masking). Round offsets to whole pixels.

Stroke-based icon (Lucide, etc.) — keep fill="none" and apply the icon color via stroke. Always use stroke-width="1.5" for Lucide:

<svg width="80" height="80" viewBox="0 0 80 80" xmlns="http://www.w3.org/2000/svg">
  <rect width="80" height="80" rx="16" fill="#FCF8F2"/>
  <g transform="translate(Xoff Yoff) scale(N)" stroke="#22D3EE" stroke-width="1.5" stroke-linecap="round" stroke-linejoin="round" fill="none">
    <!-- exact Lucide paths here, fill/stroke attributes stripped from individual paths -->
  </g>
</svg>

Filled icon — apply the icon color via fill:

<svg width="80" height="80" viewBox="0 0 80 80" xmlns="http://www.w3.org/2000/svg">
  <rect width="80" height="80" rx="16" fill="#FCF8F2"/>
  <g transform="translate(Xoff Yoff) scale(N)" fill="#22D3EE">
    <!-- source paths, individual fill attributes removed -->
  </g>
</svg>

Centering math — if the source viewBox is W × H, target inner size T = 48 (60% of 80):

• N = T / max(W, H)
• Xoff = (80 - W * N) / 2
• Yoff = (80 - H * N) / 2

Step 5 — Generate the raster source SVG

Write a second, scaled-up SVG to /tmp/favicon-source.svg — same composition, but at 512 × 512 with corner radius 102 (~20% of 512). This is the source for all PNGs and the ICO.

<svg width="512" height="512" viewBox="0 0 512 512" xmlns="http://www.w3.org/2000/svg">
  <rect width="512" height="512" rx="102" fill="#FCF8F2"/>
  <g transform="translate(Xoff Yoff) scale(N)" stroke="#22D3EE" stroke-width="1.5" stroke-linecap="round" stroke-linejoin="round" fill="none">
    <!-- source paths -->
  </g>
</svg>

For Lucide, multiply stroke-width by N if needed so it renders proportionally at large sizes, OR keep stroke-width="1.5" outside the transform and apply vector-effect="non-scaling-stroke" on the paths. Simpler: keep the icon's stroke crisp by scaling its stroke-width with N (e.g. stroke-width="${1.5 * N}").

Inner-icon target: T = 308 (~60% of 512). Same offset math as Step 4.

Step 6 — Rasterize all sizes

Run from the project root, with $PUBLIC set to the public directory (usually public):

rsvg-convert -w 512 -h 512 /tmp/favicon-source.svg -o $PUBLIC/icon.png
rsvg-convert -w 192 -h 192 /tmp/favicon-source.svg -o $PUBLIC/icon-192.png
rsvg-convert -w 180 -h 180 /tmp/favicon-source.svg -o $PUBLIC/apple-touch-icon.png
rsvg-convert -w 48  -h 48  /tmp/favicon-source.svg -o /tmp/fav-48.png
rsvg-convert -w 32  -h 32  /tmp/favicon-source.svg -o /tmp/fav-32.png
rsvg-convert -w 16  -h 16  /tmp/favicon-source.svg -o /tmp/fav-16.png
magick /tmp/fav-16.png /tmp/fav-32.png /tmp/fav-48.png $PUBLIC/favicon.ico

This produces, in public/:

• favicon.ico — multi-resolution 16/32/48 for Windows/legacy
• icon.svg and favicon.svg — the rounded square mark for modern browser tabs
• icon.png — 512×512 PNG
• icon-192.png — 192×192 PNG for Android
• apple-touch-icon.png — 180×180 PNG for iOS home screen

Step 7 — Wire up the meta tags

Edit the layout file. Inside <head>, ensure these tags exist (add or replace — do not duplicate):

<meta name="theme-color" content="#FCF8F2">
<link rel="icon" href="/favicon.ico" sizes="32x32">
<link rel="icon" href="/icon.svg" type="image/svg+xml">
<link rel="icon" href="/icon-192.png" type="image/png" sizes="192x192">
<link rel="apple-touch-icon" href="/apple-touch-icon.png">

Notes:

• theme-color uses the background color from Step 1.2.
• favicon.ico gets sizes="32x32" (not any) so modern browsers prefer the SVG.
• If the project already has a <meta name="theme-color"> or any <link rel="icon"> / apple-touch-icon, replace them — don't stack duplicates.
• Next.js app router: prefer the file convention. Drop the generated files at app/icon.svg, app/icon.png, app/apple-icon.png, app/favicon.ico (rename accordingly) and let Next emit the tags. Still write the same four files to public/ as well. Only hand-write <link> tags if the project already does.

Step 8 — Report what changed

Summarize for the user:

• The icon source used (Lucide name, library, file path, or description)
• The background and icon colors
• Which files were written
• Which head tags were added or replaced
• A reminder to hard-refresh the browser (or close and reopen the tab) to bust the favicon cache

Rules

• Do not leave behind a half-generated set. If any step fails, stop and report.
• Do not add a manifest.json unless the project already has one.
• Do not commit the changes. This skill only generates assets and edits the layout.
• Do not use emojis in file contents.
• Keep the generated SVGs minimal — no decorative comments, no unused attributes.
• Always preserve the exact Lucide path data when a Lucide icon is requested. Only the stroke width and color may change.