Knižka is a free android application developed by Brassicusa under the category of Education & Reference and subcategory of Books. The app contains basic Catholic prayers, and most of the songs from the Jednotný katolícky spevník (JKS). It also allows users to add and edit their own prayers and texts. The app has a user-friendly interface with clear categorization of prayers and songs. The latest version of Knižka (version 6.2) was released on 24 August 2016, and it fixed the issue of text display after screen rotation.

Knižka allows users to import prayers and songs from an SD card, and also provides online updates to its database. The app has a wide range of features, including the ability to change the color theme, hide the app icon, and even list prayers based on language. This app is an excellent resource for Catholics who want to have a comprehensive prayer and song book on their mobile devices.