Windows Icon Format (ICO)
Favicons (`favicon.ico`) and Windows app icons use this format. Modern favicons often use PNG inside ICO containers or switch to `<link rel="icon">` with PNG/SVG.
What It Defines
Container for one or more small raster icons at different sizes/color depths. Header: reserved (0), type (1=ICO, 2=CUR), image count, then directory entries (width, height, offset, size) pointing to embedded BMP or PNG payloads. MIME type: `image/x-icon`.
Canonical (Normative)
Convenient (Practical)
Publishes web platform specs including CSS, accessibility, security policies, Service Workers, Web App Manifest, and many browser APIs. Also maintains some versioned HTML/DOM specs.
Related Specs
PNG is the default lossless image format on the web — screenshots, UI assets, icons with transparency, and OCR-friendly graphics. Chunk structure matters for metadata stripping and security review.
Legacy Windows bitmap format still encountered in scanners, game assets, and older pipelines. Simple header + raw pixels — useful for understanding uncompressed raster layout.
The spec behind every HTML page, form, and browser API. The canonical reference for how browsers actually parse and process HTML.