The study aims to introduce catIRT tools which facilitates researchers' Item Response Theory (IRT) and Computerized Adaptive Testing (CAT) simulations. catIRT tools provides an interface for mirt and catR packages through the shiny package in R. Through this interface, researchers can apply IRT calibration and CAT simulations although they do not have any coding skills. Dichotomous and polytomous IRT models are supported in IRT calibration and Yen's Q3 statistics is calculated for the estimation of local independence. In CAT simulation, researchers can use their own parameters and responses, and can produce items or responses. In addition to several item selection and ability estimation methods, researchers can also decide on the specific stopping rule to be used.