Omni Notes is described as 'Note taking open-source application aimed to have both a simple interface but keeping smart behavior' and is a popular Note-taking tool in the office & productivity category. There are more than 100 alternatives to Omni Notes for a variety of platforms, including Android, Mac, Windows, iPhone and Web-based apps. The best Omni Notes alternative is Notesnook, which is both free and Open Source. Other great apps like Omni Notes are Zim, Trilium Notes, TiddlyWiki and CherryTree.