JNG File Format (.jng)

A JNG file holds a single still image whose colour data is compressed as baseline or progressive JPEG inside the same chunk-based container PNG uses, with an optional PNG- or JPEG-encoded alpha channel for transparency.

.jngImage Files

JNG at a glance#

Full name	JPEG Network Graphics
File extension	.jng
Category	Image Files
Developer	PNG Development Group
First released	2001
MIME types	image/x-jng
Compression	Lossy or lossless, depending on how the file was written
Specification	JNG (JPEG Network Graphics) Format Version 1.0
FileFlip support	FileFlip reads and writes this format

What a .jng file can hold#

These are the things a JNG file either supports or does not, and they are what decides whether a conversion keeps everything or quietly drops something.

Transparency (alpha channel)	Yes
Animation	No
Lossless compression	No
Embedded metadata	Yes

Strengths and limitations of JNG#

What JNG does well

Wraps ordinary JPEG-compressed colour data with a PNG-style alpha chunk, so a photographic image gets a transparent background without a fully lossless codec
Reuses PNG's chunk structure, so a parser only needs to add a JPEG decoder for the image data itself
Was designed as the photographic counterpart to MNG, letting an animation mix lossy JPEG frames with lossless PNG frames in one stream

Where JNG falls short

No browser has ever shipped native support; Mozilla removed an early implementation in 2003 and Safari never added one
Depends on the wider MNG format, which lost out to APNG and WebP for animated, transparent web images
Only a handful of programs, mainly ImageMagick, GIMP and Gwenview, still open it

There's little reason to create a new JNG file today; the format only makes sense inside an existing MNG animation that already mixes JPEG and PNG frames.

Convert JNG to JPG or PNG for anything meant to display in a browser, since none of the major browsers render JNG natively.

How to open a .jng file#

A .jng file opens in the programs below, grouped by the platform you are on. If you would rather not install anything, FileFlip converts JNG into a format your machine already opens, and it does it in the browser tab rather than on a server.

Platform	Programs that open it
Windows	ImageMagick
macOS	ImageMagick
Linux	GIMP, Gwenview, ImageMagick
Web	FileFlip

JNG questions people ask#

What opens a JNG file?

JNG files open in GIMP, Gwenview and ImageMagick-based tools, but no mainstream web browser renders them. That gap is the main reason JNG never spread beyond the small set of software built around the MNG format.

Is JNG the same thing as PNG?

No. A JNG file reuses PNG's chunk-based container but compresses its colour data as JPEG instead of PNG's lossless method, so it behaves more like a JPEG with an optional transparency layer than a true PNG. JNG exists specifically as the lossy, photographic sibling inside the MNG animation format.

Why did JNG never catch on?

JNG's fate was tied to MNG, the animated format it was built to complement, and MNG never got the browser support GIF and later APNG had. Combined with newer formats like WebP and JPEG XL covering the same lossy-plus-transparency need, JNG stayed a niche format used mainly by MNG-aware software.

Converting JNG files#

Every conversion runs inside your browser. The file is read from your disk, the work happens on your own machine, and nothing is uploaded. How FileFlip works names the engine behind each family and how to verify that for yourself.