Neo (or New or Not) Simple (or Small or Suckless) X Image Viewer.

nsxiv is a fork of now unmaintained sxiv with the purpose of being a drop-in
replacement of sxiv, maintaining it and adding simple, sensible features.
nsxiv is free software licensed under GPLv2 and aims to be easy to modify
and customize.

Homepage:
https://nsxiv.codeberg.page/
