The UQ Toolkit (UQTk) is a collection of libraries and tools for the quantification of uncertainty in numerical model predictions. UQTk offers intrusive and non-intrusive methods for propagating input uncertainties through computational models, tools for sensitivity analysis, methods for sparse surrogate construction, and Bayesian inference tools for inferring parameters from experimental data. UQTk is written mainly in C++ and can be linked to an application code for direct access to its functionality. Standalone C++ apps, as well as a Python wrapper PyUQTk are also provided to access UQTk from the command line or shell scripts.

UQTk is designed primarily for rapid prototyping, UQ tutorials, and algorithmic design. As such, it is used in various DOE ASCR SciDAC application partnership projects including climate modeling and fusion energy sciences. It is also used in the DOE BER E3SM earth system modeling effort as well as in DARPA-funded work on UQ in supersonic turbulent reacting flow. UQTk has about 200 downloads per year.