World Wide Web Consortium Issues First Recommendation for PNG

Author(s) and publish date


PNG Delivers Higher Quality Graphics for Web Page Design

Testimonials | Fact Sheet


Cambridge, Massachusetts, USA -- October 7, 1996 -- Responding to a need for faster loading, enhanced quality cross-platform Web graphics, The World Wide Web Consortium (W3C) today endorsed the Portable Network Graphics (PNG) specification as a W3C Recommendation. This means that the specification is stable, contributes toward the W3C mission of 'Realizing the Full Potential of the Web', and that W3C Members have reviewed it and are in favor of supporting its adoption by the industry.

PNG answers the need of the Web page design community for cross-platform Web graphics. PNG offers particular advantages for brand recognition, product design, medical applications, fine art and on-line catalogs, where visual quality is important. PNG provides information in the file about the characteristics of the authoring platform, so that the viewing software can automatically compensate and display the image correctly.

"PNG is a significant advancement in Web graphical design and we are excited about the possibilities that it promises," said Tim Berners-Lee, director of the World Web Consortium and creator of the World Wide Web. "The W3C is working to enhance the user interface; we are confident that PNG provides the best lossless format for Web graphical design available today. We are seeing more of our Members adopt the format and are helping make it the industry standard."

"Designers routinely use variable transparency when creating images for print," explained Chris Lilley, the W3C's graphics lead. "But up to now, only crude on-or-off transparency has been available on the Web which has led to jagged images that did not blend into the background, or images with undesirable white haloes. PNG offers optional full transparency, enabling content with partially transparent overlaid images which will display correctly over any background color or texture."

The development of the PNG specification was supported by W3C and by CompuServe - original creators of the GIF format and now W3C Members - who both wished to see PNG become accepted as the new Internet standard format for lossless graphics.

(Please see attached PNG fact sheet and testimonials document for additional information on PNG.)

World Wide Web Consortium

The W3C was created to develop common standards for the evolution of the World Wide Web. It is an industry consortium jointly run by the MIT Laboratory for Computer Science (LCS) in the USA, the National Institute for Research in Computer Science and Automation (INRIA) in France and Keio University in Japan. Services provided by the Consortium include: a repository of information about the World Wide Web for developers and users; reference code implementations to embody and promote standards; and various prototype and sample applications to demonstrate use of new technology. To date over 150 organizations are Members of the Consortium.

MIT Laboratory for Computer Science

Now in its third decade, MIT LCS is dedicated to the invention, development and understanding of information technologies expected to drive substantial technical and socio-economic change. The LCS has helped information technology grow from a mere curiosity to 10 percent of the industrial world's economies by its pioneering efforts in interactive computing, computer networking, distributed systems and public key cryptography. LCS members and alumni have started some thirty companies and have pioneered the Nubus, the X-Window System, the RSA algorithm, the Ethernet and spreadsheets.

Instiut National de Recherche en Informatique et en Automatique

INRIA, the French National Institute for Research in Computer Science and Automation, is a public-sector scientific institute charged with conducting both fundemental and applied research, and with transferring research results to industry. INRIA is made up of five Research Units located at Rocquencourt (near Paris), Rennes, Sophia Antipolis, Nancy and Grenoble. Areas of current research include information processing, advanced high speed networking, structured documents, and scientific computation.

Keio University

Keio University is one of Japan's foremost computer science research centers and universities. It is one of the oldest private universities in Japan, and has five major campuses around Tokyo. Keio University has been promoting joint research projects in cooperation with industry, government and international organizations, and is now becoming one of the research leaders for the network and digital media technology.

Further information on the World Wide Web Consortium is available via the Web at

For information on PNG in particular, see


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PNG Testimonials


"A major concern to Agfa is maintaining color fidelity throughout the image processing chain, i.e. from photograph, through scanning, to viewing on screen and to final print. Therefore any standard that helps realizing this goal in an open systems environment has our fullest support. The International Color Consortium, of which Agfa is a founding member, recently standardized color usage within operating systems. Clearly a similar effort is required for the world wide web community. We believe that by defining the new "Portable Network Graphics" format, the W3C has taken this crucial step forward."

-- Dirk De Baer, R&D Manager Color Management, Agfa


"DigitalStyle's WebSuite was one of the first commercial products to support the PNG graphics format standard. WebSuite enables 'graphically challenged' users to create and add custom, professional quality graphics to their web sites. Features such as drop shadows, anti-aliasing, variable opacity, etc. are one-click away for users. WebSuite uses PNG for its internal storage, enabling the user to manipulate multiple graphical layers with full alpha support, something that is impossible using the graphic standards in use on the web today, notably GIF and JPG. Widespread support of PNG will enable WebSuite users to take advantage of the more powerful features of PNG to create graphically-richer web graphics and sites.

-- Jim Hamerly, President and CEO, DigitalStyle Corporation


"PNG is the breakthrough in color imaging on the web that finally allows everyday users to easily display high-quality images on their web pages. HP and Microsoft are particularly please to have PNG support sRGB in its effort to accurately communicate color across the web."

-- Michael Stokes, Project Manager, Color Research, Hewlett-Packard Research Laboratories; Chairman, International Color Consortium


Microsoft Office 97 uses Portable Network Graphics (PNG) as it's native lossless compressed graphic image format. PNG allows us to drastically reduce the size of files that contain graphics and allows us to implement transparency in our new OfficeArt drawing component. Since PNG is a small and platform independent format, Office users can easily exchange graphical documents across the web"

-- Jon DeVaan, Vice President of Office product development, Microsoft Corporation


"The PNG format from the W3C is a great image format for the World Wide Web. This free and open standard helps address a need for better image support on the web with lossless compression, well implemented transparency support, platform independence and color management features like support for sRGB. sRGB is a calibrated RGB that Microsoft and HP designed together as a step towards efficient color management on the web."

-- John Ludwig, Vice President, Internet Platform and Tools, Microsoft Corporation


"SoftQuad is pleased with the PNG specification. Software products which conform to the PNG specification are seen to be interoperable. SoftQuad HoTMetaL PRO 3.0 includes a graphics editor which includes support for the PNG format, and SoftQuad intends to provide ongoing support for the PNG format in its electronic publishing software products."

-- Murray Maloney, Technical Director, SoftQuad, Inc.

PNG Fact Sheet


Responding to a need for faster loading, enhanced quality cross-platform Web graphics, The World Wide Web Consortium (W3C) recently issued the Portable Network Graphics (PNG) specification as a W3C Recommendation.

Designed to set a new quality standard for lossless images, PNG provides small files and rapid previews to enhance the responsiveness of Web pages, and to enable graphics to look the same on different platforms. Of particular value to designers who use variable transparency when creating images for print, PNG permits similar effects on the Web -- partially transparent overlaid images to be displayed over any background color or texture, eliminating white haloes.

The PNG format was created in December 1994 and has been stable since March 1995. Since then, the specification has become much more readable and has gained valuable tutorial and developer information. Simultaneously, acceptance of PNG has grown, viewers have appeared on many different platforms, content creation tools have appeared with PNG support, and browsers are starting to support PNG images inline.

Key Characteristics & Benefits

Cross-platform Interoperability

Automatic gamma correction across platforms means that PNG files can be correctly displayed on Macs, PCs, SGI workstations, etc. (all of which have different gamma values) without appearing either too light and insipid or too dark and contrasty. Storing the source gamma used by the image author is the simplest way of helping interoperability with the biggest payoff. Chromaticity data can also be stored in PNG files and can be used by Color Management Systems on the viewing platform to compensate for differing monitor types; an important ability where precise color matching is required - brand recognition, product design, medical applications, fine art and on-line catalogs, for example.

Smaller, Faster Loading Files

In practice, indexed color PNG files average about 30% smaller than the equivalent GIF, and truecolor PNG files are 30-40% smaller than the equivalent (LZW compressed) RGB TIFF.

The advanced interlacing scheme gives a preview image after only 1/64th of the image data has been loaded (as opposed to 1/8th with GIF), and small details are recognizable much sooner than with an interlaced GIF image. In tests, it was found that five of the seven passes were retrieved and displayed in the same time as the first pass of interlaced GIF.

Metadata for Searching and Indexing

PNG files can contain keywords and text strings, which can be extracted by Web search tools and used to locate images on the Web. For example, a picture might have a description of "Sunset behind Edinburgh Castle, with Piper in foreground." A search on sunset and castle would locate this image; a search on Edinburgh and not piper would reject it, which is much easier than trying to guess based on the filename. Standard keywords include: Title, Author, Description, and Copyright. More specialized applications can define their own keywords. Lengthy text, such as legal disclaimers, can be compressed.


PNG is an extensible file format for the lossless, portable, well-compressed storage of single raster images. It is not a competitor for JPEG JFIF, which is an excellent format for lossy storage of suitable pictures.

PNG is a good choice for those truecolor images which are unsuited to JPEG compression, such as raytraced images.

PNG can also be used for greyscale images and for indexed (palette) images. PNG is a good choice for images that have transparency information. PNG can be used to store up to 16 bits of greyscale information, or 48 bits of color information, making it suitable as an output format from graphics arts scanners, medical equipment, and scientific applications.

Compression is asymmetric - decompression for viewing is quite fast, at the expense of longer compression time when the image is created - because images on the Web are read by many people, but only written once.

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