The performance of a model can be evaluated by its learnability from data and generalizability on unseen datasets, performed through internal and external validation, respectively. Internal validation (IV) involves cross-validation techniques for training models and hyperparameter tuning. External validation (EV), on the other hand, utilizes a validation dataset from an independent source to assess the model's performance unbiasedly. As such, the results of EV provide crucial evidence for the generalizability of a QSAR model 27 .