Portable Network Graphics (MIME: image/png) is a lossless image format that supports transparency, making it the go-to choice for web graphics, logos, icons, and images requiring sharp edges or transparent backgrounds.
History and Development
PNG (Portable Network Graphics) was created in 1996 as a patent-free replacement for GIF, after Unisys began enforcing the LZW compression patent used in GIF. It was standardized as ISO/IEC 15948 in 2004. PNG introduced lossless compression with full alpha transparency — features GIF could not match. The APNG (Animated PNG) extension was later developed by Mozilla in 2008 to add animation support.
Technical Specifications
- Compression: Lossless (DEFLATE algorithm)
- Color depth: 1-bit to 48-bit (truecolor) or 16-bit grayscale
- Transparency: Full alpha channel (256 levels)
- Max resolution: 2,147,483,647 × 2,147,483,647 pixels (theoretical)
- Animation: Via APNG extension (not part of original spec)
- Interlacing: Adam7 interlacing for progressive display
- Metadata: tEXt/iTXt chunks, limited EXIF support
- Color spaces: sRGB, grayscale, indexed color (palette)
Common Use Cases
PNG excels at logos, icons, UI elements, screenshots, diagrams, and any image with text or sharp edges. Web developers use PNG for images requiring transparency (overlays, badges). It's the standard format for app icons and favicons. Screenshots are typically saved as PNG because lossless compression preserves text clarity.
PNG vs Similar Formats
- PNG vs JPEG: PNG is lossless with transparency; JPEG is much smaller for photos. Use PNG for graphics, JPEG for photographs.
- PNG vs WebP: WebP offers lossless compression at 26% smaller files than PNG, with both transparency and animation support.
- PNG vs SVG: SVG is vector-based (infinitely scalable) while PNG is raster. Use SVG for logos and icons that need to scale; PNG for complex images.
How to Open and Edit
PNG files are universally supported across all operating systems and browsers. Edit with Photoshop, GIMP, Figma, or any image editor. For web optimization, use tools like TinyPNG (lossy PNG optimization) or pngquant to reduce file size while maintaining transparency.
Frequently Asked Questions
Why are PNG files so large?
PNG uses lossless compression, meaning no visual data is discarded. A photograph saved as PNG can be 5-10x larger than the same image as JPEG. Use PNG only when you need lossless quality or transparency.
Does PNG support animation?
Standard PNG does not support animation. APNG (Animated PNG) is an extension that adds animation with full alpha transparency, supported by all modern browsers since 2020.
When should I use PNG over JPEG?
Use PNG when you need: (1) transparent backgrounds, (2) sharp text or line art, (3) lossless quality for editing, or (4) screenshots. For photographs, JPEG is usually better.