Vega and Vega-Lite are visualization tools implementing a grammar of graphics, similar to ggplot2. The Vega and Vega-Lite grammars extend Leland Wilkinson's Grammar of Graphics[2] by adding a novel grammar of interactivity to assist in the exploration of complex datasets.
Vega acts as a low-level language suited to explanatory figures (the same use case as D3.js), while Vega-Lite
is a higher-level language suited to rapidly exploring data.[3] Vega is used in the back end of several data visualization systems, for example Voyager.[4][5] Chart specifications are written in JSON and rendered in a browser or exported to either vector or bitmap images. Bindings for Vega-Lite have been written in several programming languages, such as the Python package Altair,[6] to make it easier to use. The grammars and associated tools are open source projects led by the University of Washington Interactive Data Lab and released under a BSD-3 license.[7]