VisIt is an open-source, interactive parallel visualization, and graphical analysis tool designed for viewing scientific data.

Being open-source and released under the BSD license, VisIt has received contributions from various other developers[citation needed].

The application serves as an infrastructure for parallelized, general post-processing of extremely massive data sets.

However, an alternate form exists where a simulation code can link in "lib-VisIt" and become itself the server, allowing for in situ visualization and analysis.

VisIt follows a data flow network paradigm where interoperable modules are connected to perform custom analysis.