Plena Vortaro is a Chrome add-on developed by Jan Michalak. It is a free program that falls under the category of Browsers and the subcategory of Add-ons & Tools.

This add-on provides an unofficial extension to the Plena Ilustrita Vortaro (PIV) for Esperanto. With Plena Vortaro, users can simply select a word and a window will appear with its definitions. Users can also view definitions of words from within the windows. If users click elsewhere, the windows will disappear.

Plena Vortaro allows users to customize the add-on according to their preferences or disable it through a pop-up window. Please note that the add-on only functions when there is an active internet connection and it does not work in input fields.