Open the JPG image file you want to convert into an icon. With the plugin, you merely need to save the file with the file extension of .ico to create the icon.

Find an extension who's icon you want to change, and swap out the icon_19.png file with the icon you found online. When you restart Chrome, your new icon should show up in its place.

Icons use the ICO file extension, but due to file formatting issues, it won't work to simply change the file extension of a JPEG file to ICO.

An icon file is a format in which icons of various sizes are stored in ".ico" file which is one extension, and the background is transparent.