W3C: REC-png.html

PNG (Portable Network Graphics) Specification

Version 1.0

W3C Recommendation 01-October-1996

For list of authors, see Credits.

Status of this document

This document has been reviewed by W3C members and other interested parties and has been endorsed by the Director as a W3C Recommendation. It is a stable document and may be used as reference material or cited as a normative reference from another document. W3C's role in making the Recommendation is to draw attention to the specification and to promote its widespread deployment. This enhances the functionality and interoperability of the Web.

A list of current W3C Recommendations and other technical documents can be found at http://www.w3.org/TR/.

The Consortium staff have encouraged the development of PNG, as have Compuserve, Inc. Most of the work has been done by the PNG Development Group, png-group@w3.org. The Consortium does not currently have plans to work on any future versions of PNG, though were the necessity to arise, and were an activity in that area to receive the support of Members, the Consortium could in principle support some future activity.


This document describes PNG (Portable Network Graphics), an extensible file format for the lossless, portable, well-compressed storage of raster images. PNG provides a patent-free replacement for GIF and can also replace many common uses of TIFF. Indexed-color, grayscale, 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 gamma and chromaticity data for improved color matching on heterogeneous platforms.

This specification defines a proposed Internet Media Type image/png.

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