ICO vs PNG: Which Format for Favicons and Icons?
Published on April 2, 2026
ICO is a container format that holds multiple bitmap images at different sizes (16x16, 32x32, 48x48, 256x256) in a single file. PNG is a standard image format with lossless compression and full alpha transparency. For modern favicons, PNG is the better choice for most websites. ICO is still needed as a fallback for older browsers and certain Windows desktop applications.
How They Work
An ICO file is essentially a bundle. Inside it, you can pack 16x16, 32x32, 48x48, and 256x256 pixel versions of your icon. The browser or operating system picks the best size for the context. A 16x16 version appears in browser tabs, while the 48x48 version shows up in Windows taskbar shortcuts. PNG files contain only one image at one size. If you need multiple sizes, you create multiple PNG files and reference each one with a separate link tag in your HTML.
File Size
A multi-size ICO file containing 16x16, 32x32, and 48x48 versions runs 5-15 KB total. A single 32x32 PNG favicon is typically 1-3 KB because of its efficient compression algorithm. If you add up three separate PNG files at different sizes, the total is often less than the equivalent ICO. PNG compression is simply better than what ICO uses internally, which is uncompressed BMP data for sizes below 256x256.
Browser and Platform Support
Every modern browser (Chrome, Firefox, Safari, Edge) supports PNG favicons. Internet Explorer 10 and below only supports ICO, but IE market share is effectively zero in 2026. Windows desktop shortcuts and some native applications still prefer ICO because the operating system can extract the right size automatically. macOS uses ICNS (its own icon format) rather than ICO, and Linux desktops generally use PNG or SVG.
Quality and Transparency
PNG supports full 8-bit alpha transparency, allowing smooth edges and semi-transparent effects. ICO also supports transparency, but its internal BMP format uses 1-bit alpha (fully transparent or fully opaque) for sizes below 256x256. The 256x256 layer in modern ICO files actually stores a PNG internally, so at that size they are identical. For small icons with clean edges, this difference is invisible. For icons with gradients or shadows, PNG renders better.
Best Practice for Favicons
Use a 32x32 PNG as your primary favicon with a link tag in your HTML head. Add a favicon.ico file at your site root as a fallback. The ICO should contain 16x16 and 32x32 versions. Also include a 180x180 PNG for Apple touch icons and a 192x192 PNG for Android. This covers every browser and device with minimal effort.
Working with icons and need format conversion? Our PNG to JPG converter handles batch processing. For more image format breakdowns, see PNG vs JPG, SVG vs PNG, and WebP vs PNG.