Files with the JPG extension are compressed raster image files stored in JPEG format (Joint Photographic Experts Group). JPG extension is used interchangeably with JPEG. JPEG is a lossy compression method, which means that during storing a file, some part of information is permanently lost.
ICNS is a system file format used by macOS. ICNS files store various icons used by applications. Each application can have its own icon file packages, typically saved in the Contents/Resources/ directory. References to ICNS files are also listed in PLIST files.
After converting the file to the new format, you will be able to use other programs to support it. Keep in mind, however, that the JPG file after converting to ICNS may differ slightly from the original. The most important information should be kept, but if you want the file after conversion from JPG to ICNS to be the same, you have to do this carefully and choose the proper application from the list below.
There is no guarantee, of course, that the conversion will come up to all your expectations, but it will certainly help you. If, after all, the effect of converting JPG to ICNS does not meet your expectations, you can simply try to find on the Internet a different version of your file in JPG format, properly converted to a ICNS file by someone else. If this fails, use the information provided in the further part of the website.
If after converting the file JPG the desired result was not achieved, you can try to change the format of JPG file to other than ICNS. On our website you will find more information on the following conversion options
Unfortunately, if after performing the two previously described steps (trying to find your JPG file converted by someone else, and the attempt to convert it to ICNS on your own) you still have a problem with your file, then there are only a few solutions left. You can once again try to find and install an application that can open the JPG file in its original format (without conversion to ICNS file). Such a solution will be difficult to implement, but it certainly will give the best result.