Wydźwięk is an open-access system used to process and analyze texts in Polish in order to annotate the data with emotional overtones using basic types of emotions and universal values ​​assigned to words. This tool can be used to define the nature of the analyzed texts by indicating the positive or negative aspect of the textual data. The analysis of emotional overtone may be applicable in various areas, such as marketing (e.g. monitoring the overtone of customer opinions), e-commerce (e.g. grouping products, detecting anomalies in descriptions, recommendations), politics (e.g. tracking voters’ reactions), or as an element of scientific research (e.g. research on subjective information of Polish texts from social media).