ICO Format Guide & Converter

Windows Icon is a Windows icon container that can hold multiple raster sizes for app and favicon use, introduced by Microsoft (1990s). ICO packages one or more bitmaps (and sometimes PNGs) so Windows and browsers can pick the right resolution for a shortcut or favicon. Design in PNG/SVG first, then build an ICO when a platform still requires the classic container.

Full name

Windows Icon

Kind

raster image

File extension

.ico

MIME type

image/x-icon

Developer / standard

Microsoft · 1990s

Compression

varies

Quality model

Lossless / not lossy

Container

No / single bitstream typical

Common codecs

—

Technical sources

—

Transparency

Supported

Animation

No (still / non-animated typical use)

Typical size

Small — usually under a few hundred KB

Browser support

Favicon ICO is widely requested; not used as a general <img> format

Compatibility

Native on Windows; browsers still request /favicon.ico on many sites

ICO compression: varies. Lossless (or non-destructive packaging) keeps reconstructable data — size savings come from packing efficiency, not throwing detail away. Typical size profile: Small — usually under a few hundred KB. Quality note: Depends on embedded sizes; include crisp 16–256 px assets

Quality: Depends on embedded sizes; include crisp 16–256 px assets

Typical size: Small — usually under a few hundred KB

ICO supports transparency (including alpha where the codec/container allows). Keep a format with alpha when you need soft edges or overlays.

ICO is a still-media or non-animated format in typical use. Use GIF, APNG, video, or animated WebP when you need motion.

Commonly supports EXIF, IPTC, and/or XMP depending on encoder (camera make, GPS, orientation, color profile). Strip metadata before public sharing if privacy matters.

Related tools: image metadata viewer · metadata remover

• Windows application icons
• Classic favicon.ico for websites
• Shortcut and installer branding
• Multi-resolution desktop icons

• General photo storage
• Print graphics
• Responsive hero images
• Situations where SVG or PNG alone is enough

• Multiple sizes in one file
• Expected by Windows tooling
• Familiar favicon convention
• Can embed PNG-compressed images in modern ICOs

• Awkward to edit compared with SVG/PNG
• Easy to ship blurry if sizes are missing
• Not a general web content image
• Over-specified for sites that only need PNG favicons

Native on Windows; browsers still request /favicon.ico on many sites

Browsers: Favicon ICO is widely requested; not used as a general <img> format

• IcoFX
• GIMP
• Photoshop with plugins
• Format Convertly
• Build tooling

• Windows desktops
• Browsers fetching favicons

Windows shows ICO on executables and shortcuts. Inspect contents with an icon editor. Browsers load favicon.ico automatically when linked.

Start from a sharp PNG, then use Format Convertly’s ICO converters in-browser to produce a shareable icon without uploading your brand assets.

• Pick a target format from popular conversions or the full list below.
• Your file is read into browser memory — not uploaded to a server.
• Download the result when conversion finishes.

Incoming conversions strengthen the ICO cluster — e.g. JPG → ICO, PNG → ICO.

Tools extend the format graph beyond one-off conversion — compression, metadata, and utilities for real workflows.

Uploading sensitive ICO files to a random converter creates a third-party copy you cannot control. Format Convertly keeps processing on-device so photos, contracts, and exports stay private.