# What's the default Scorer in Sci-kit learn's GridSearchCV?

Even if I don't define the scoring parameter, it scores and makes a decision for best estimator, but documentation says the default value for scoring is "None", so what is it using to score when I don't define a metric or list of metrics?

By default, parameter search uses the score function of the estimator to evaluate a parameter setting. These are the sklearn.metrics.accuracy_score for classification and sklearn.metrics.r2_score for regression...
• Each estimator's score docstring says what it measures. But classifiers and regressors consistently use accuracy and r2, respectively. May 12, 2021 at 1:13