The ratio between the heavy and light stable isotopes in precipitation is an effective tool for addressing questions in e.g., hydrology, climatology, biogeochemistry etc., but only if spatiotemporally sufficient data is available from precipitation monitoring networks. However, when data from multiple sources are gathered into large databases these can contain errors severely impacting research outcomes. The most common practices for stable isotopic database filtering apply static thresholds, not accounting for the spatially dynamically changing nature of the variable. We propose a distance-based outlier detection approach in the form of an online tool. The IsoQC App is developed to identify likely-outliers or inconsistent data points by deriving adjustable elevation-corrected average isotope values for nearby stations within an adjustable search radius (0 < R ≤ 500 km). The IsoQC is showcased on the records of the precipitation stable isotope network of Slovenia and its vicinity. It enables an objective and reproducible analysis of spatial and temporal patterns of nearby precipitation stable isotopic records by employing thresholds for dissimilarity between regional averages and individual station records in a dynamic graphical user interface. The interactive nature of the application allows users to explore spatial and temporal variations in precipitation isotope compositions, identify anomalous data points, and empirically assess regional isotope patterns in real time. The developed IsoQC tool is freely available at https://sapps.geochem.hu/isoqc/