I noticed that XML files were previewing but JSON files were not, in the right-most column of Finder windows, in column view mode. I searched and found this repo, and installed all using the brew cask method in the readme.
Now, when I use the spacebar to quick view, I can see XML and JSON content just fine, but in the Finder window itself, in the right-most column, I only get the piece of paper with curled corner image, for JSON and XML. (Oddly, the piece of paper is narrower for JSON files...)
macOS High Sierra 10.13.1 (17B48)
I noticed that XML files were previewing but JSON files were not, in the right-most column of Finder windows, in column view mode. I searched and found this repo, and installed all using the brew cask method in the readme. Now, when I use the spacebar to quick view, I can see XML and JSON content just fine, but in the Finder window itself, in the right-most column, I only get the piece of paper with curled corner image, for JSON and XML. (Oddly, the piece of paper is narrower for JSON files...)