Updated Candidate Recommendation: Portable Network Graphics (PNG) Specification (Third Edition)

The Portable Network Graphics (PNG) Working Group invites implementations of an updated Candidate Recommendation Snapshot of Portable Network Graphics (PNG) Specification (Third Edition). This document describes PNG (Portable Network Graphics), an extensible file format for the lossless, portable, well-compressed storage of static and animated raster images. PNG provides a patent-free replacement for GIF and can also replace many common uses of TIFF. Indexed-color, greyscale, and truecolor images are supported, plus an optional alpha channel. Sample depths range from 1 to 16 bits.

PNG is designed to work well in online viewing applications, such as the World Wide Web, so it is fully streamable with a progressive display option. PNG is robust, providing both full file integrity checking and simple detection of common transmission errors. Also, PNG can store color space data for improved color matching on heterogeneous platforms.

This specification defines two Internet Media Types, image/png and image/apng.

Comments are welcome via the GitHub issues by 13 May 2025.