The MNG file (.mng, .jng)

When PNG was designed in 1995 as a free replacement for GIF, its authors left animation out to keep the format simple. MNG, Multiple-image Network Graphics, was the companion format for everything else: animations, sequences of images and composited scenes, built from the same chunks as PNG. The PNG Development Group approved MNG version 1.0 on 31 January 2001.

MNG aimed far beyond GIF. Frames could be lossless PNG images with full alpha transparency, or JPEG-compressed JNG images for photos. A file could loop sections, move and clip images, paste one image into another, magnify, and store only the changes between frames as delta-PNG images. In effect it was a small animation language.

That ambition is also why it faded. A complete MNG decoder was large and complicated, few programs supported it, and browsers removed what support they had. Today MNG is a legacy format: you'll meet it in old software, games and archives, while new animations use GIF, APNG, animated WebP or video.

An MNG datastream starts with MHDR, ends with MEND, and in between holds objects (embedded images) and control chunks that say when and where to show them. The main chunks from the specification:

Timing works in ticks. MHDR gives the number of ticks per second, and FRAM chunks give delays in ticks. With no FRAM chunks, as in the example above, a viewer shows one frame per tick.

Because full MNG was so demanding, the PNG group defined two subsets that simpler decoders could support. The MHDR simplicity profile, a 32-bit field, tells a decoder which features a file uses before it starts.

The MNG files ImageMagick writes from a list of frames, like the example above, are simple sequences of this kind: their profile of 1 rules out every optional feature.

MNG briefly had a foothold in browsers: Netscape 6 and 7 and the Mozilla suite displayed it natively, as did early versions of KDE's Konqueror. On 3 June 2003, Mozilla removed MNG and JNG support (bug 195280), citing the size of the code and how little the format was used. The decision drew protests from MNG's developers and users, but it stuck, and no other major browser ever added MNG.

In 2004, two Mozilla developers, Stuart Parmenter and Vladimir Vukićević, proposed APNG instead: animation added to an ordinary PNG file with a few extra chunks, so old software still shows the first frame. The PNG Development Group rejected APNG as an official extension in 2007, but Firefox 3 shipped it in 2008, Chrome followed with version 59 in 2017, and the W3C's PNG third edition made it part of the PNG standard in 2025. MNG, meanwhile, became obsolete.

• Complexity: a complete MNG decoder was a large library; APNG adds only a handful of chunks to what a PNG decoder already does.
• Compatibility: an MNG file is unreadable to PNG software; an APNG file is still a valid PNG.
• Timing: by the time MNG was finished in 2001, animated GIF was already everywhere, and the GIF patents expired soon after.

For a new animation, use GIF where it must work everywhere, APNG (PNG) or WebP for better quality, or an MP4 video for anything long.

• View it: XnView, IrfanView (with its plug-ins) and KDE's Gwenview open MNG files; MPlayer plays them when built with libmng. No current browser displays them.
• Convert to GIF: magick animation.mng animation.gif keeps the frames and their timing, reduced to 256 colours per frame.
• Extract the frames: magick animation.mng frame-%02d.png writes one PNG per frame.
• Make an APNG: extract the frames, then join them with ffmpeg, giving the frame rate: ffmpeg -framerate 5 -i frame-%02d.png -plays 0 animation.apng. Rename the result to .png if you like; it's a valid PNG either way.
• Inspect one: identify animation.mng lists the frames, and a hex dump shows the chunks, since each type is four readable letters.

• Nothing shows in the browser. No current browser supports MNG. Convert it to GIF, APNG or WebP.
• Only one frame appears. The viewer reads MNG as a still image, or handles only part of the format. Try ImageMagick or XnView, or extract the frames.
• The file won't open at all. It may use full-MNG features, such as delta-PNG or JNG, that a simple decoder skips. The simplicity profile in MHDR says which ones.
• Colours change after converting to GIF. GIF allows only 256 colours per frame and no partial transparency. Convert to APNG or WebP to keep them.
• Old decoders and untrusted files. Like any old, rarely used image library, an unmaintained MNG decoder is a risk with files from unknown sources. Convert them in an up-to-date tool.