Understanding favicons
The smallest icon on the internet.
Why a single tab icon turned into a sprawling family of sizes — and what you actually need to ship today.
The original 16×16.
Internet Explorer 5 introduced favicon.ico in 1999. Browsers looked for a 16×16 ICO file at the site root and showed it next to the address bar. It was a happy accident — there was no spec, just a convention — and twenty years later every browser still asks for it. A modern favicon set has grown to include high-DPI versions, app icons for mobile home screens, tile icons for Windows, monochrome icons for taskbars, and an SVG that scales to any size.
favicon.ico + apple-touch-icon + svg + manifest
The modern minimum.
For 2026 you need: a 32×32 PNG (the universal browser tab), a 180×180 PNG named apple-touch-icon.png (iOS home screen), an SVG favicon (Chrome and Firefox use it for crisp scaling), and a Web App Manifest pointing at 192 and 512 PNGs (used on Android home screens and PWA install screens). Browsers fall back gracefully — ship the SVG and the 180 and you'll cover almost everything.
SVG favicons.
Modern browsers accept an SVG via <link rel="icon" type="image/svg+xml">. The advantage is one file scales for every density without aliasing. The catch: the SVG should be drawn for tiny sizes — fine details disappear at 16px and you'll find yourself designing two versions anyway. Hint at colour mode with prefers-color-scheme media queries inside the SVG so the icon flips for dark-mode chrome.
The 60-pixel rule.
Apple touch icons sit on a glass-like square; iOS rounds the corners and slightly insets the artwork. Apple's guidance: design the artwork to use about 60 of 76 (or the equivalent ratio at 180×180) so nothing important sits where the corner radius might clip it. The Android adaptive icon has the same idea — your artwork is the foreground layer, and the home screen launcher chooses how to mask it.
The ICO format, briefly.
ICO is a small container that can hold multiple images at different sizes — 16, 32, 48 historically. The browser picks the closest match. Generators today bundle 16 and 32; older IE versions also wanted 48 for taskbar pins, which is mostly historical now. PNG inside ICO is supported by every modern system; the older bitmap format is no longer needed.
Cache busting.
Browsers cache favicons aggressively — sometimes for the life of the install. A favicon that changed yesterday may show the old version for hours or days. The reliable fix is to change the URL: append a query string (favicon.ico?v=2) or rename the file outright. The first time a browser sees the new URL, it has no cached entry, and the new icon paints immediately.
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