Graphics Interchange Format (GIF)
GIF remains common for short animated loops and legacy assets. GIF89a extension blocks enable animation timing and transparent pixels.
What It Defines
Palette-based raster format supporting animation and transparency. Header: `GIF87a` or `GIF89a` magic, logical screen descriptor, optional global color table, then image blocks and animation control extensions. MIME type: `image/gif`.
Canonical (Normative)
Related References
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
Every upload, download, attachment, and asset pipeline crosses these layers. Misunderstanding header vs envelope causes MIME spoofing bugs, parser differentials, and broken file validation. Start here before diving into individual format 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.
WebP delivers smaller files than JPEG/PNG for equivalent quality — widely used for web delivery via `<picture>`, CDN transforms, and Next.js image optimization.