.JLS File Extension

In 1999, the Joint Photographic Experts Group (JPEG) released an addition to the original JPEG standard, describing a compression format that allowed programs to save images both losslessly and near-losslessly. That compression format and its associated file format were named JPEG-LS. Notably, JPEG-LS compression allows users to control the maximum amount of data that is lost when a program compresses their image, which is what makes the lossy version of the format "near-lossless."

While JPEG-LS files are saved using the .jls extension, other file formats, such as .JPX and .SPIFF, also sometimes use JPEG-LS compression. JPEG-LS and JPEG, however, are different file formats, so programs that can open a .JPEG or .JPG often cannot open JLS files.

Most popular image viewing applications cannot open JLS files. However, you can open a JLS image in Irfanview (Windows) and XNView MP (cross-platform), and you can convert a JLS image to a more usable image format using NConvert (cross-platform).