Librus Średnia is a free Chrome add-on developed by Christopher Kwiatkowski. It falls under the category of Browsers and is specifically classified as an Add-ons & Tools subcategory.

The main function of Librus Średnia is to display the average grade for each subject, even though this feature has been disabled by the school administrator. In version 2.0.X, the add-on offers several features to enhance the user experience. It displays the average grade for each subject in a table, as well as the overall average at the bottom of the table. It also provides the average for mid-term and annual grades, along with the predicted mid-term and annual grades.

Additionally, Librus Średnia automatically closes the "Behavior" field in the table and allows users to customize the calculation parameters for the average grade in the add-on settings. The add-on intelligently adjusts the number of columns in the table and synchronizes settings across browsers when the user is logged in (if the browser supports synchronization).

Overall, Librus Średnia is a useful Chrome add-on for students who want to easily view their average grades for each subject in the Librus platform.