Overview

image/png is the media type for raster images losslessly compressed with PNG (Portable Network Graphics). It supports alpha transparency and preserves sharp edges exactly, making it ideal for logos, icons, screenshots, and UI graphics.

Details

PNG uses DEFLATE-based lossless compression, so re-saving does not degrade quality, and it supports everything from 8-bit palettes to truecolor with an alpha channel. Its lossless, transparent nature is ideal for graphics with text or assets needing a transparent background. Conversely, for photograph-like continuous-tone images, files are larger than JPEG or WebP.

As already-compressed binary, transport-layer gzip barely helps. Instead, tools like pngquant and oxipng reduce palettes and optimize, or you negotiate via `Accept` to prefer WebP/AVIF that store the same quality smaller, with PNG as fallback — better for web performance. APNG extends PNG for animation but has limited support.

Syntax

e.g. Content-Type: image/png

File extensions

Notes

• PNG is inefficient for photos (large files) — prefer JPEG, WebP, or AVIF for continuous-tone images.
• Being lossless, re-encoding causes no quality loss, but size optimization requires separate tools (e.g. pngquant).
• Already compressed, so transport gzip barely helps; handle optimization in the image pipeline.

Related types

Related headers